A noun appearing as G. uimoth “a whale” in the Gnomish Lexicon of the 1910s, literally meaning “sheep of the waves”, a combination of G. uin “†wave” and G. moth “sheep” (GL/74). In the Gnomish Lexicon, the sense “wave” for uin was marked as archaic (†), and it also came to mean “whale” in ordinary speech after the name of the great whale Uin.
Neo-Sindarin: For purposes of Neo-Sindarin, I would update this word to ᴺS. gwimmaf “whale”, a combination of gwing “foam” and [ᴺS.] maf “sheep”.
This word only appears in the name of the Númenórean ship Turuphanto “Wooden-whale” (UT/191). The language of the name is unclear, but Carl Hostetter suggested (Tolklang/5.31) that the name is likely to be Quenya, since ᴱQ. turu meant “wood”. If so, the second element phanto might be Quenya for “whale”. This spelling is unusual, however. In Quenya, [f] was normally spelled “f”, while the spelling “ph” appeared only in languages like Sindarin or Adûnaic.
Conceptual Development: The only other attested words for “whale” are the very early G. uin and G. uimoth in the Gnomish Lexicon (GL/74).