ᴱN. ach n. “waterfall” (Category: Brook, Stream, River)
In the Gnomish Lexicon of the 1910s, Tolkien had G. acha “waterfall” as a cognate to ᴱQ. aksa (GL/17). Its form became âch in Gnomish Lexicon Slips adding to that document (PE13/108) and ach in Early Noldorin Word-lists from the 1920s (PE13/136, 158).
References ✧ PE13/136, 158
References ✧ GL/17; LT1A/Asgon; PE13/108
|ᴱ√aksa > acha||[aksā] > [aksa] > [acha]||✧ GL/17|