In early and mordern folklore, they became associated with the fairies of Romance folklore and assume a diminutive size, often living mainly in forests but also underground in hills or rocks, or in wells and springs. 19th-century Romanticism attempted to restore them to full stature making them men and women of great beauty. They were often depicted as very young, probably adolescents as male elves lack of facial hair.
From thair depiction in Romanticism, elves entered the 20th-century high fantasy genre in the wake of the published work of J. R. R. Tolkien (especially the posthumous publication of his Silmarillion where Tolkien's treatment of the relation of light elves, dark elves and dwarves is made explict).
The "Christmas elves" of contemporary pop culture were popularized during the 1870's in the United States, in publications such as Godey's Lady's Book.
The English word elf is from the Old English ælf or elf, in reference to a midget, themselves from the Proto-Germanic *albiz which also resulted in Old Norse álfr, Middle High German elbe. *Albiz may be from the Proto-Indo-European root *albh- meaning "white", from which also stems the Latin albus "white". Alternatively, a connection to the Rbhus, semi-divine craftsmen in Indian mythology, has also been suggested.
Originally ælf/elf and its plural ælfe were the masculine forms, while the corresponding feminine form (first found in eighth century glosses) was ælfen or elfen (with a possible feminine plural -ælfa, found in dunælfa) which became the Middle English elven, using the feminine suffix -en from the earlier -inn which derives from the Proto-Germanic *-innja). The fact that cognates exist (such as the German elbinne) could suggest a West Germanic *alb(i)innjo, but this is uncertain, as the examples may be simply a transference to the weak declension common in Southern and Western forms of Middle English. The Middle English forms with this weak declension were aluen(e) and eluen(e). By the earlier eleventh century ælf could denote a female.
The Modern German Elf (m), Elfe (f), Elfen is a loan from English. A masculine Elb is reconstructed from the plural by Jacob Grimm, Deutsches Wörterbuch, who rejects Elfe as a (then, in the 1830s) recent anglicism. Elb (m, plural Elbe or Elben) is a reconstructed term, while Elbe (f) is attested in Middle High German. Alb, Alp (m), plural Alpe has the meaning of "incubus" (Old High German alp, plural *alpî or *elpî). Gothic has no direct testimony of *albs, plural *albeis, but Procopius has the personal name Albila.
Jacob Grimm discusses "Wights and Elves" comparatively in chapter 17 of his Teutonic Mythology. He notes that the Elder Edda couples the Æsir and the álfar, a conjunction that recurs in Old English ês and ylfe, clearly grouping the elves as a divine or supernatural class of beings, sometimes extended by the Vanir as a third class: The Hrafnagaldr states Alföðr orkar, álfar skilja, vanir vita "The Allfather [i.e. the áss] has power, the álfar have skill, and vanir knowledge".
A notable crux in the Old Norse mythology is the distinction of álfar and dvergar. They appear as separate races in extended lists such as the one in Alvíssmál, listing Æsir, álfar, Vanir, goð (gods), męnn (humans), ginregin, jǫtnar, dvergar and denizens of Hęl. Middle High German tradition asgma separates the elbe from getwerc.
On the other hand, there is a close kinship between elves and dwarves, evident already because many dwarves have elvish names, including simple Álfr "elf", and Alberich "king of elves".
Loki is particularly difficult to classify; he is usually called an áss, but is really of jǫtunn origin, and is nevertheless also addressed as álfr. The conclusion of Grimm is that the classification "elf" can be considered to "shrink and stretch by turns". The etymology connecting *alboz with albus "white" suggests an original dichotomy of "white" vs. "black" genii, corresponding to the elves vs. the dwarves which was subsequently confused. Thus the "white" elves proper are named ljósálfar "light elves", contrasting with døckálfar "dark elves".
Snorri in the Prose Edda states that the light elves dwell in Álfheim while the dark elves dwell underground. Confusion arises from the introduction of the additional term svartálfar "black elves", which at first appears synonymous to the "dark elves"; Snorri identifies with the dvergar and has them reside in Svartálfaheim. This prompts Grimm to assume a tripartite division of light elves, dark elves and black elves, of which only the latter are identical with dwarves, while the dark elves are an intermediate class, "not so much downright black, as dim, dingy". In support of such an intermediate class between light elves, or "elves proper", on one hand, and black elves or dwarves on the other, Grimm adduces the evidence of the Scottish brownies and other traditions of dwarves wearing grey or brown clothing.
The earliest preserved descriptions of elves comes from Norse mythology. In Old Norse they are called álfar (nominative singular álfr).
Men could be elevated to the rank of elves after death, such as the petty king Olaf Geirstad-Elf. The smith hero Völundr is identified as 'Ruler of Elves' (vísi álfa) and 'One among the Elven Folk' (álfa ljóði), in the poem Völundarkviða, whose later prose introduction also identifies him as the son of a king of 'Finnar', an Arctic people respected for their shamanic magic (most likely, the sami). In the Thidrek's Saga a human queen is surprised to learn that the lover who has made her pregnant is an elf and not a man. In the saga of Hrolf Kraki a king named Helgi rapes and impregnates an elf-woman clad in silk who is the most beautiful woman he has ever seen.
Crossbreeding was possible between elves and humans in the Old Norse belief. The human queen who had an elvish lover bore the hero Högni, and the elf-woman who was raped by Helgi bore Skuld, who married Hjörvard, Hrólfr Kraki's killer. The saga of Hrolf Kraki adds that since Skuld was half-elven, she was very skilled in witchcraft (seiðr), and this to the point that she was almost invincible in battle. When her warriors fell, she made them rise again to continue fighting. The only way to defeat her was to capture her before she could summon her armies, which included elvish warriors.
They are also found in the Heimskringla and in The Saga of Thorstein, Viking's Son accounts of a line of local kings who ruled over Álfheim, and since they had elven blood they were said to be more beautiful than most men.
The land governed by King Alf was called Alfheim, and all his offspring are related to the elves. They were fairer than any other people..
In addition to these human aspects, they are commonly described as semi-divine beings associated with fertility and the cult of the ancestors and ancestor worship. The notion of elves thus appears similar to the animistic belief in spirits of nature and of the deceased, common to nearly all human religions; this is also true for the Old Norse belief in dísir, fylgjur and vörðar ("follower" and "warden" spirits, respectively). Like spirits, the elves were not bound by physical limitations and could pass through walls and doors in the manner of ghosts, which happens in Norna-Gests þáttr.
The Icelandic mythographer and historian Snorri Sturluson referred to dwarves (dvergar) as "dark-elves" (dökkálfar) or "black-elves" (svartálfar). He referred to other elves as "light-elves" (ljósálfar), which has often been associated with elves' connection with Freyr, the god of fertility (according to Grímnismál, Poetic Edda). Snorri describes the elf differences as follows:
"There is one place there that is called the Elf Home (Álfheimr which is the elven city). People live there that are named the light elves (Ljósálfar). But the dark elves (Dökkálfar) live below in earth,in caves and the dark forest and they are unlike them in appearance – and more unlike them in reality. The Light Elves are brighter than the sun in appearance, but the Dark Elves are blacker than pitch." (Snorri, Gylfaginning 17, Prose Edda) "Sá er einn staðr þar, er kallaðr er Álfheimr. Þar byggvir fólk þat, er Ljósálfar heita, en Dökkálfar búa niðri í jörðu, ok eru þeir ólíkir þeim sýnum ok miklu ólíkari reyndum. Ljósálfar eru fegri en sól sýnum, en Dökkálfar eru svartari en bik." Further evidence for elves in Norse mythology comes from Skaldic poetry, the Poetic Edda and legendary sagas. In these elves are linked to the Æsir, particularly by the common phrase "Æsir and the elves". In the Alvíssmál ("The Sayings of All-Wise"), elves are considered distinct from both the Æsir and the Vanir.
Grímnismál relates that the Van Frey was the lord of Álfheimr (meaning "elf-world"), the home of the light-elves. Lokasenna relates that a large group of Æsir and elves had assembled at Ægir's court for a banquet.
A poem from around 1020, the Austrfaravísur ('Eastern-journey verses') of Sigvat Thordarson, mentions that, as a Christian, he was refused board in a heathen household, in Sweden, because an álfablót ("elves' sacrifice") was being conducted there.
From the time of year (close to the autumnal equinox) and the elves' association with fertility and the ancestors, it might be assumed that it had to do with the ancestor cult and the life force of the family.