Savo.

A shortening of earlier Savoilahti, Savoinlahti (attested as Sawolax in 1323), the latter part of which is lahti (“bay, gulf”), earlier laksi (thus Swedish Savolax, from *Savoi(n)laksi). The name is almost certainly related to Savilahti (after which a bailiwick and later the region was named) which is likely simply savi (“clay”) + lahti (“bay, gulf”), with the -o representing a diminutive ending (from *-oi), possibly through a demonym savolainen. Other theories associate the name with Sami words for “stream pool” (Proto-Samic *sëvōn, Northern Sami savu), with an Eastern Finnish given name Savo (compare the Veps given name Savoi), from Russian Савва (Savva), Савва́тий (Savvátij), and a Western Finnish given name Sauvo (possibly akin to saukko). These given names could perhaps be more relevant as sources for the surname than for the place name at large, although the surname probably mostly derives from the place name.