vapouryoudaoicibaDictYouDict
vapour: [14] Latin vapor meant ‘steam, heat’. English acquired it via Old French vapour. The now archaic use of the plural, vapours, for a ‘fit of fainting, hysteria, etc’, which dates from the 17th century, was inspired by the notion that exhalations from the stomach and other internal organs affected the brain. Vapid [17] comes from Latin vapidus ‘insipid’, which may have been related to vapor.
=> vapid
faint (v.)youdaoicibaDictYouDict
c. 1300, "grow weak, become enfeebled," also "lack courage or spirit, be faint-hearted," and "to pretend, feign;" from faint (adj.). Sense of "swoon, lose consciousness" is from c. 1400. Also used in Middle English of the fading of colors, flowers, etc. Related: Fainted; fainting. For Chaucer and Shakespeare, also a transitive verb ("It faints me").
syncope (n.)youdaoicibaDictYouDict
1520s, "contraction of a word by omission of middle sounds or letters," from Latin syncope "contraction of a word by elision," from Greek synkope "contraction of a word," originally "a cutting off, cutting up, cutting short," from synkoptein "to cut up," from syn- "together, thoroughly" (see syn-) + koptein "to cut," from PIE root *kop- "to beat, strike" (see hatchet (n.)).

An earlier use of the word in pathology is represented by Middle English syncopis, sincopin "loss of consciousness accompanied by weak pulse" (c. 1400, from Late Latin accusative syncopen); compare Old French syncope "illness, fainting fit" ("failure of the heart's action," hence "unconsciousness"). The spelling of this was re-Latinized 16c. Related: Syncopic; syncoptic.
vapor (n.)youdaoicibaDictYouDict
late 14c., from Anglo-French vapour, Old French vapor "moisture, vapor" (13c., Modern French vapeur) and directly from Latin vaporem (nominative vapor) "a warm exhalation, steam, heat," of unknown origin. Vapors "fit of fainting, hysteria, etc." is 1660s, from medieval notion of "exhalations" from the stomach or other organs affecting the brain.