"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 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.
"worthless thing, disappointment, booby prize," 1909, American English slang; from lemon (n.1), perhaps via a criminal slang sense of "a person who is a loser, a simpleton," perhaps an image of someone a sharper can "suck the juice out of." A pool hall hustle was called a lemon game (1908); while to hand someone a lemon was British slang (1906) for "to pass off a sub-standard article as a good one." Or it simply may be a metaphor for something which leaves a bad taste in one's mouth. Specific sense of "second-hand car in poor condition" is by 1931.