Meaning

noun fictional character created by Charles Dickens; an eternal optimist

originA name likely coined by Charles Dickens, evidently reminiscent of common Irish, Scots, and Scottish Gaelic surnames starting with Mc-, Mac-, both from Old Irish macc (“son, child”) (see more there). For the second particle, compare names like Aubrey; similar surnames like M(a)cAubrey are attested around Dickens' time and thus Micawber may represent a dialectal variation.

Etymology from Wiktionary, CC BY-SA 3.0