"resembling or infused with lemon," 1846, from lemon (n.1) + -y (2). In Australia/New Zealand slang, also "irritated, angry" (1941). An earlier adjective was lemonish (1719).
Entries linking to lemony
lemon n.1
"ovate, pale yellow citrus fruit," c. 1400, lymon, from Old French limon "citrus fruit" (12c.), which comes via Provençal or Italian from Arabic laimun, Persian limun. Apparently brought from India to the Levant by the Arabs 9c. or 10c.; the word is perhaps ultimately from an Austronesian word of the Malay archipelago, such as Balinese limo "lemon," Malay limaw "citrus fruit, lime" (compare lime (n.2)).
Meaning "person with a tart disposition" is from 1863. For the sense "worthless thing," see lemon (n.2). Slang meaning "a Quaalude" is 1960s, from Lemmon, name of a pharmaceutical company that once manufactured the drug. The surname is from Middle English leman "sweetheart, lover." Lemon-juice is attested from 1610s; the candy lemon-drop from 1807. The East Indian lemon-grass (1837) is so called for its smell.
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.