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).
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).