Etymology
1. The adjective is derived from Late Middle English musty; further origin uncertain, possibly from one of the following:
2. * From Anglo-Norman muste, moste, variants of moiste, muiste (“moist”), from Old French moiste (“clammy, damp, moist, wet”) (modern French moite (“muggy; sticky, sweaty”)), from a blend of Vulgar Latin *mucidus (from Latin mūcidus (“mouldy, musty”), from Old Latin mūceō (“to be mouldy or musty”) + -idus (suffix meaning ‘tending to’, forming adjectives)) + Latin mustum (“unfermented or partially fermented grape juice, must; new wine”) (from mustus (“fresh; young; unfermented”), from Proto-Indo-European *mus-, *mews- (“damp; moss”)).
3. * From another language derived from the above Latin words (compare the cognates below).
4. * A variant of Middle English mosty, moisti (“damp, humid, wet, moisty; of fruit: moist and juicy”) [and other forms] (perhaps influenced by must (“fruit (usually grape) juice which has been or will be fermented”)), from moist, moiste (“damp, humid; moist, wet; well-irrigated, well-watered; liquid; of ale: new; (figuratively) not withered, fresh; carnal, lascivious; raw, undisciplined”) (from Old French moiste: see above) + -i (suffix forming adjectives).
5. Compare Middle French moisi (“mouldy”), an adjective use of the past participle of moisir (“(to cause) to go mouldy, to moulder”) (modern French moisir), from Latin mūcēre, the present active infinitive of Old Latin mūceō (“to be mouldy or musty”): see above.
6. The English word is analysable as must (“mould; mustiness”) + -y (suffix meaning ‘having the quality of’ forming adjectives); however, must is thought to be a back-formation from musty.
7. The noun and verb are derived from the adjective.
8. Cognates
9. * Catalan mústic, musti (“wilted, withered; gloomy, sad”)
10. * Galician murcho, mucho (“wilted, withered”)
11. * Old Occitan moste (Occitan moste, mosti, musti (“damp, wet”) (Gascon))
12. * Portuguese murcho (“wilted, withered; gloomy, sad”)
13. * Spanish mustio (“wilted, withered; gloomy, sad”) See: French Adjectives '
moite', Latin Adjectives '
mūcidus', Catalan Adjectives '
mústic', Galician Adjectives '
murcho', Portuguese Adjectives '
murcho', Spanish Adjectives '
mustio'.