A verb appearing as N. sautha- “drain” in The Etymologies of the 1930s under the root ᴹ√SUK “drink” (Ety/SUK), probably from primitive *sukta- where (a) the u became o before a, (b) the combination okt vocalized to outh and then (c) the ou became au.

Conceptual Development: The verb G. soctha- “give to drink, quench” in the Gnomish Lexicon of the 1910s seems to be similarly derived from sokta- based on the early root ᴱ√SOKO “drink” (GL/68), but Gnomish did not have the same kind of vocalizations as later Noldorin and Sindarin.

Neo-Sindarin: There is evidence that in Sindarin of the 1950s and 60s, the vocalization of okt was oith rather than outh so that the result would instead be soitha- > *soetha-. However, I prefer to assume the existence of dialectical variations in the Sindarin of the First Age with differing vocalizations, and thus would retain the form sautha- myself.