出典:Wiktionary
From Middle English flakeren (“to flutter, waver”), from 古期英語 *flacorian, from Proto-West Germanic *flakurōn, from Proto-Germanic *flakurōną (“to flutter”), related to 古期英語 flacor (“flickering, fluttering”). Sometimes regarded as a frequentative, equivalent to flack + -er (frequentative suffix).
Akin to Middle Dutch flakkeren (“to flicker, waver”), German flackern (“to flare, flicker, flutter”), Icelandic flökra (“to flutter”), Icelandic flakka (“to rove about”), 古期英語 flacor (“flying, fluttering”). See also flack, flicker.