Meaning

noun a hat tied under the chin

noun protective covering consisting of a metal part that covers the engine

verb dress in a bonnet

originFrom Middle English bonet, from Middle French bonet (Modern French bonnet), from Old French bonet (“material from which hats are made”), from Frankish *bunni (“that which is bound”), from Proto-Germanic *bundiją (“bundle”), from Proto-Indo-European *bʰendʰ- (“to tie”). Compare also Late Latin abbonis, obbonis (“ribbon of a headdress”), also of Germanic origin, from Frankish *obbunni, from *ob-…

Etymology from Wiktionary, CC BY-SA 3.0