boon (n.) Look up boon at Dictionary.com
late 12c., bone "a petition, a prayer," from Old Norse bon "a petition, prayer," from Proto-Germanic *boniz (source also of Old English ben "prayer, petition," bannan "to summon;" see ban (v.)). The sense gradually passed from "favor asked" to "thing asked for," to "a good thing received, a benefit enjoyed" (1767).
boon (adj.) Look up boon at Dictionary.com
in boon companion "convivial friend, close intimate" (1560s), the only real survival of Middle English boon "good" (early 14c.), from Old French bon (see bon), from Latin bonus "good" (see bonus). Probably influenced by boon (n.).