出典:Wiktionary
From Middle English wansen (“to decrease, diminish”), from 古期英語 wansian (“to diminish”), from Proto-Germanic *wansōną, *wanisōną (“to lessen”), from Proto-Indo-European *h₁weh₂- (“empty”). Cognate with Old Norse vansa (“to do too little”), Old Norse vansi (“lack, want”). More at wane.