Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
DOW
As described in historical dictionaries
Patronymica Britannica (1860)
DOW. Probably a corruption of the Gaelic, Dint, i.e. black; but doK or doo, the Scottish for dove or pigeon, may be the origin. Dow, without prefix, is found in H.R. It also appears to have been a personal name, and to ha\e given rise to Dowson, Dowse, Dowsing, and Dowsett, and also to the local name Dowsby in Lincolnshire.
Origin: Celtic
Region of origin: British Isles
Country of origin: Scotland
Religion of origin: Christian
Language of origin: Gaelic