Elendil masc. name"Star-friend", "Lover or student of stars", applied to those devoted to astronomical lore. However, when the Edain used this name they intended it to mean "Elf-friend", confusing elen "star" and elda "elf" (WJ:410). (This idea that the name was misapplied seems to be late; Tolken earlier interpreted the name as an ancient compound Eled + ndil so that the meaning really was "Elf-friend"; see Letters:386. See also NIL/NDIL in the Etymologies, where Elendil is equated with "Ælfwine", Elf-friend.) Allative Elendilenna "to Elendil" (PM:401); Elendil Vorondo genitive of Elendil Voronda "Elendil the Steadfast" _(CO) Pl. Elendili the Númenórean Elf-friends (Silm)_; the variant Elendilli in SD:403 would seem to presuppose a stem-form Elendill- not attested elsewhere. Tar-Elendil a Númenorean king, UT:210.
elendilmasculine name. Ælfwine, Elf-friend, Elf-friend, Elf-friend, Star-lover, Elf-friend; lover or student of the stars
Tar-Elendil was the fourth ruler of Númenor (UTI/219). Many centuries later a second, more famous, Elendil became the leader of the Men of the West against Sauron at the end of the Second Age and was considered the first king of Gondor and Arnor (LotR/1037). This name is attributed two different meanings: “Elf-friend” and “Star-lover” (WJ/410). The first interpretation was common among Men, and was derived from the ancient associations between Elda “Elf” and †él “star”. Properly speaking, though, his name was a compound of elen “star” and the suffix -(n)dil “lover”, so “Star-lover” is a better interpretation in proper Quenya. The proper Quenya for “Elf-friend” would be Eldandil.
Conceptual Development: In the very first draft of the tale of the Fall of Númenor, this character was named N. Agaldor > N. Amroth (LR/12, 31). When this character first appeared in the “Lost Road”, his name was ᴹQ. Herendil “Fortune’s Friend” and his father was called ᴹQ. Elendil (LR/57). In “The Notion Club Papers”, the character was given the Adûnaic name Ad. Nimruzân >> Nimruzîr “Elf-friend” (SD/389-90), and his contemporaneous Quenya name also shifted to ᴹQ. Elendil (SD/356). His father became ᴹQ. Amardil, later Q. Amandil.
The earlier character Ælfwine might be consider a precursor to Elendil, at least in the meaning of his name: “Elf-friend”. Therefore, the early Qenya name ᴱQ. Eldairon of Ælfwine could be considered a precursor to the name Elendil (LT2/313).
Eldandil (pl. Eldandili in WJ:412) noun "Elf-friend" (by the Edain confused with Elendil, properly "Star-friend") (WJ:410)
Quendendil (also contracted Quendil; pl. Quendili in WJ:410) masc. name "Elf-friend" (WJ:410)
-dil, -ndil, ending that Tolkien likened to Old English "-wine", sc. "-friend" as part of names, e.g. Elendil, Eärendil (NIL/NDIL); see the entry -ndil. Also long -dildo (VT46:4), and possibly -(n)dilmë as the corresponding feminine form (see Vardilmë).
-nil, final element in compounds, similar in meaning to Old English "-wine", sc. "-friend" as an element in names (NIL/NDIL). Also long -nildo (VT46:4). Variant of -ndil. In Eärnil, contraction of Earendil.
Elessar masc. name "Elf-stone" (Elen + sar, actually "Star-stone", cf. Elendil concerning elen "star" being used to mean "Elf") (LotR3:V ch. 8). Genitive Elesarno _(VT49:28, read _Elessarno?) indicates that the stem is -sarn-. As a common noun, elessar or "elf-stone" may signify "beryl" (in the chapter Flight to the Ford in the LotR, Aragorn finds "a single pale-green jewel" and declares: "It is a beryl, an elf-stone"). Elessar as a name may also be seen as a pun or variant of Elesser "Elf-friend".