Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
SWAIN
As described in historical dictionaries
Patronymica Britannica (1860)
B° SWAIN. The A-Sax. swcui, a pastoral servant, and the Scand. Sweyn, a proper name originally of the same import, have impressed themselves upon many localities, which in their turn have given designations to families. Among those which do not occur in gazetteers are Swainston, Swainsland (now Swaysland), Swanstou, and others.
Origin: English
Region of origin: British Isles
Country of origin: England
Religion of origin: Christian
Language of origin: English