晕倒
yūn dǎo · HSK 7
to faint
😵💫 晕 = dizzy + 倒 = fall over; get dizzy then topple = faint
晕 (yūn) means dizzy or giddy; 倒 (dǎo) means to fall or topple. Stack them and you get the dizzy-then-collapse sequence of fainting. The yūn part also shows up in 头晕, to feel dizzy.
晕 — sun 日 on top + army/chariot 軍 (jūn) below
Originally a phono-semantic compound: 日 (sun) gives the meaning of a hazy halo or ring of light around the sun or moon, while 軍 hints at the sound. From 'solar/lunar halo' it extended to 'dizzy, faint, giddy,' as if one's vision were ringed and blurred.
倒 — person radical 亻 + 到 (to arrive)
倒 is a semantic-phonetic compound: the person radical 亻 gives meaning (an action done by/to a person), while 到 supplies the sound 'dào'. Originally meaning 'to fall over' (a person toppling), it extended to 'invert, upside down, pour out', as when something falls and spills.