Douglas is the anglicized form of Scottish surname Dubhghlas meaning “dark river” or “dark stream”, composed of Scottish Gaelic dubh (black) and glais (water; green). It comes from the name of a river in Scotland from which the name of the clan Douglas derives its name from.
Interestingly, Douglas was originally used as a unisex name in the early 17th and 18th century but eventually it only became used as a male name.
Neva is a female name with a variety of meanings and origins such as:
it could be a shortened form of Geneva, the name of a city in Switzerland (also spelled Genava in Latin). Though the etymology behind the name is uncertain, it’s often been linked to a Celtic word deriving from a PIE root word genu (bend), in the sense of a bending river or an estuary;
it’s also possible that Geneva could be used as a shortened form of Genevieve, which comes from French Geneviève, derived from medieval name Genovefa, a name of uncertain etymology. The first part of the name has been linked to Germanic *kunją (kin, family, clan) though it’s also possible it may derive from Celtic *genos (family, clan; birth), which both derive from the same PIE origin. The second part of the name comes from Proto-Germanic *wībą (woman; wife) though another possible source may be Common Celtic *wihu- (worthy, valuable) via Proto-Celtic *wesus (excellent, noble);
Neva is also the name of a river that runs from Russia to the Gulf of Finland. The name could be derived from Finnish nevo meaning “sea” though I’ve also seen it listed as coming from Finnish neva meaning “marsh”. Another possible origin is Swedish ny via Old Norse nýr meaning “new”, but those are all debatable;
Neva is also a Finnish surname, a topographical name meaning “marsh” though it also means “waterway” in Karelian ( a type of Finnic language spoken in Karelia, located in Russia, and is closely related to Finnish);
I’ve also seen it listed as possibly meaning “snow”, which I’m guessing is somehow based on the Spanish word for snow; Nevada, the name of an American state, is based on Spanish meaning “snow; snow-covered”, so Neva could be based or used as a shortened form of it.
Meaning: a shortened form of Geneva, linked to a Celtic word meaning “bend”, as in a bending river or an estuary; perhaps a shortened form of Genevieve perhaps meaning “woman of the family” or “born worthy”; also the name of a river that runs from Russia through Finland, of uncertain etymology; also a Finnish surname “marsh”, “waterway”; might possibly be related to the Spanish word for “snow”