A title of Oromë as the Lord of Forests (S/29). The name is genitive plural of alda “tree”, so its literal meaning is “Of Trees”.
Conceptual Development: This name was well established in Tolkien’s lengendarium, appearing as ᴱQ. Aldaron “King of Forests” in the earliest Lost Tales (LT1/66) and in later stories as ᴹQ. Aldaron “Lord of Forests” (SM/79, LR/206), always having the same basic meaning and form. This name appeared in the published version of The Silmarillion, but according to Christopher Tolkien, his father deleted this name from the final version of the “Valaquenta”, leaving only S. Tauron (MR/202, notes §8). A shorter form Aldar appeared in linguistic notes from the 1950s (PE22/86), though whether this form was intended to be a name of Oromë is unclear.
The basic Quenya word for “tree” (LotR/1113), derived from primitive ✶galadā and very well attested. This word dates all the way back to the Qenya Lexicon of the 1910s where ᴱQ. alda “tree” appeared under the early root ᴱ√ALA “spread” (QL/29). Tolkien seems to have switched its derivation to ✱galadā in The Etymologies of the 1930s, where ᴹQ. alda “tree” appeared under the root ᴹ√GALAD of the same meaning (Ety/GALAD). See also ornë “(tall) tree” for a discussion of another similar word.
Conceptual Development: There were a few instances where the word alda had a different meaning. In Early Qenya Word-lists of the 1920s, alda was glossed “branch” (PE16/139). In notes from 1959 Tolkien said “✱galadā, originally only large flourishing plant, as tree, and especially one that flowered, Q alda, S galað; the general word for ‘tree’ was Q orne ‘upstanding plant’ (PE17/153)”. But in its numerous appearance elsewhere, alda was simply a general word for “tree”.