Boss
early 19th century (originally US): from Dutch baas ‘master’.
wiktionary
From Dutch baas, from Middle Dutch baes(“master of a household, friend”), from Old Dutch *baso(“uncle, kinsman”), from Proto-Germanic *baswô, masculine form of Proto-Germanic *baswǭ(“father's sister, aunt, cousin”). Cognate with Middle Low German bās(“supervisor, foreman”), Old Frisian bas(“master”), hence Saterland Frisian Boas(“boss”), Old High German basa(“father's sister, cousin”), hence German Base(“aunt, cousin”).
Originally a term of respect used to address an older relative. Later, in New Amsterdam, it began to mean a person in charge who is not a master. The representation of Dutch -aa- by English -o- is due to the older unrounded pronunciation of this letter, which is still used in North America and parts of Ireland, but was formerly found in some British accents as well.
The video game sense is borrowed from Japanese ボス(bosu).
From Middle English bos, bose, boce, from Old French boce(“lump, bulge, protuberance, knot”), from Frankish *bottja, from Proto-Germanic *bautaną(“to hit, strike, beat”). Doublet of beat; see there for more.
Apparently a corruption of bass.
etymonline
boss (n.1)
"overseer, one who employs or oversees workers," 1640s, American English, from Dutch baas "a master," Middle Dutch baes, of obscure origin. If original sense was "uncle," perhaps it is related to Old High German basa "aunt," but some sources discount this theory.
The Dutch form baas is attested in English from 1620s as the standard title of a Dutch ship's captain. The word's popularity in U.S. may reflect egalitarian avoidance of master (n.) as well as the need to distinguish slave from free labor. The slang adjective meaning "excellent" is recorded in 1880s, revived, apparently independently, in teen and jazz slang in 1950s.
boss (n.2)
"protuberance, button," c. 1300, from Old French boce "a hump, swelling, tumor" (12c., Modern French bosse), from either Frankish *botija or Vulgar Latin *bottia, both of uncertain origin.
boss (v.1)
"be master or manager of, to order and direct as a boss," 1856, from boss (n.1). Related: Bossed; bossing.
boss (v.2)
c. 1400, "to swell out; to beat or press into a raised ornament," from boss (n.2). From 1620s as "to furnish with bosses." Related: Bossed; bossing.
