A verb in the Gnomish Lexicon of the 1910s appearing as G. {sûtha- >> sû- “wash clean” and sôtha- “bathe (tr. & intr.)” >>} sô- “wash clean, bathe (tr. & intr.)”, all based on the early root ᴱ√soƀ (GL/68). Likely the long ô is the result of the sound change whereby ou became ō as was usual in Gnomish of the 1910s.
Neo-Sindarin: In later Sindarin ancient ou became ū which produces problematic verb forms, so I would instead adapt this verb as ᴺS. sov- “to wash clean, bathe” as a cognate to ᴺQ. sov- “✱to bathe”. See also ᴺS. whal- “to wash”.
A noun appearing as G. sû “noise of wind” in the Gnomish Lexicon of the 1910s (GL/68), probably derived from the early root ᴱ√SUHYU “air, breath, exhale, puff” as suggested by Christopher Tolkien (LT1A/Súlimo; QL/86).
Neo-Sindarin: Since Q. sú “sound of wind” appears in Tolkien’s later writings (VT47/12), I think ᴺS. sû “noise of wind” still works for Neo-Sindarin.