boon (adj.) Look up boon at Dictionary.com
in boon companion (1560s), only real survival of Middle English boon "good" (early 14c.), from Old French bon (see bon).
boon (n.) Look up boon at Dictionary.com
late 12c., bone "petition," from Old Norse bon "a petition, prayer," from Proto-Germanic *boniz (cognates: Old English ben "prayer, petition," bannan "to summon;" see ban).