köken: From Middle Persian 𐫉𐫏𐫏𐫃 (zyyg /zīg/), 𐫉𐫙𐫏𐫃 (zʿyg /zīg/), alternative form of zyh (zīh, “cord; bowstring”), whence Persian زه (zeh, “cord; bowstring”). The former word has also been borrowed as Arabic زِيج (zīj), زِيق (zīq) and from this Persian زیج (zij).
köken: Change in meaning from 陽炎 (kagerō, “heat haze, heat shimmer”), from the way that the insects fly in swarms that visually resemble heat haze. The kanji is jukujikun (熟(じゅく)字(じ)訓(くん)), from Chinese 蜉蝣 (fúyóu).
mayfly (insect) · living day-to-day, without future plans or money; someone who lives in such a way · something ephemeral
köken: Compound of 하루 (haru, “one day”) + 살— (sal-, “to live”) + -이 (-i, agentive noun-deriving suffix). First attested in the Hunmong jahoe (訓蒙字會 / 훈몽자회), 1527, as Middle Korean ᄒᆞᄅᆞ사리〮 (Yale: hòlòsàlí).