buoyyoudaoicibaDictYouDict[buoy 词源字典]
buoy: [13] Buoy is of disputed origin, as to both its immediate source and its ultimate derivation. One school of thought holds that English borrowed it directly from Old French boie ‘chain’, while another views Middle Dutch boeye as an intermediate stage. Again some etymologists maintain that its beginnings were amongst the Germanic languages, and have connected it with English beacon, while others would trace it via Latin boia ‘strap’ to Greek boeiai ‘ox-leather straps’, a derivative of bous ‘ox’ (which is related to English cow).

The meaning of Old French boie favours the latter explanation, the semantic link being that buoys are held in place by chains. Buoyant [16] comes from Spanish boyante, the present participle of boyar ‘float’, which was derived from boya ‘buoy’, a borrowing from Old French boie.
[buoy etymology, buoy origin, 英语词源]
buoy (n.)youdaoicibaDictYouDict
late 13c., perhaps from either Old French buie or Middle Dutch boeye, both from West Germanic *baukna "beacon, signal" (see beacon). OED, however, supports Middle Dutch boeie, or Old French boie "fetter, chain" (see boy), "because of its being fettered to a spot."
buoy (v.)youdaoicibaDictYouDict
late 16c., "to mark with a buoy," from buoy (n.). Meaning "rise up, lift, sustain" is from c. 1600, perhaps influenced by Spanish boyar "to float," ultimately from the same source. In the figurative sense (of hopes, spirits, etc.) it is recorded from 1640s. Related: Buoyed; buoying.