An Etymological Dictionary of the German Language/Annotated/Sohle
Sohle (1.), feminine, Modern High German only, formed like the equivalent English sole, Swedish sola, from the Latin-Romance term solea, ‘flat fish’; compare French sole, Italian soglia. Is the term Scholle (Dutch schol) derived from the same source?
Sohle (2.), feminine, ‘sole (of the foot),’ from the equivalent Middle High German sol, sole, Old High German sola, feminine; borrowed contemporaneously with Socke prior to the Old High German period from Latin *sŏla (a variant of sŏlea), which is implied by Italian suolo, French sole, ‘sole.’ Latin sŏlea, whence Italian soglia, French seuil, ‘threshold,’ is probably the source of Gothic sulja, ‘sole.’ The primary kinship of Old High German sola with Latin solea (Greek ὑλιώ) is conceivable if Schwelle is allied.