family name (late 12c.), later masc. personal name, from Gaelic Dubh glas "the dark water," name of a place in Lanarkshire. Douglas fir named for David Douglas (1798-1834), Scottish botanist who first recorded it in Pacific Northwest, 1825. Douglas scheme, Douglas plan, Douglassite, etc. refer to "social credit" economic model put forth by British engineer Maj. Clifford Hugh Douglas (1879-1952).