A root in The Etymologies of the 1930s glossed “joy, be glad” that is an extension of ᴹ√GALA “thrive” (Ety/GALAS). Its two most notable derivatives were ᴹQ. alasse and N. glass “joy”. The appearance of Q. alassë “happiness” in the so-called “Merin Sentence” (MS), probably written after the publication of The Lord of the Rings, indicates that this root may have remained valid.
Middle Primitive Elvish
galā-
verb. to grow
galad
root. tree
galas
root. joy, be glad
golā-
verb. to grow
gal
root. grow, thrive
galadā
noun. tree
ol
root. grow
The basis for Elvish “tree” words, this root first appeared in The Etymologies of the 1930s as an extension of ᴹ√GALA “thrive” (Ety/GALAD). This replaced the earliest derivation of “tree” from the Qenya Lexicon of the 1910s, where the Qenya word for “tree” ᴱQ. alda was derived from ᴱ√ALA “spread” (QL/29). In The Etymologies, the Quenya form of this word remained the same, but the 1910s Gnomish words G. âl “wood” and †alwen “tree” (GL/19) became the 1930s Noldorin word N. galadh “tree” (Ety/GALA). Quenya and Sindarin retained these words for “tree” thereafter, and while Tolkien did not mention the root √GALAD again, his continued use of primitive ✶galadā “tree” (Let/426; PE17/153; PE21/74; UT/266) made it clear this root remained valid.