Crossword Dictionary
imbecile
imbecile, imbeciles - n
a mentally deficient person
If your best friend calls you an imbecile, he's implying that you're stupid, and he's probably pretty angry with you. An imbecile is an extremely stupid person.
The noun imbecile is used informally as an insult to mean "fool". Its origins are in the Latin word imbecille, "weak or feeble," and it was an official medical term for people with a specific (and low) I.Q. in the 19th and early 20th centuries. Patients who were classified as imbeciles were said to have no more intelligence than a seven year-old child.
etymology
1540s, imbecille "weak, feeble" (especially in reference to the body), from French imbecile "weak, feeble" (15c.), from Latin imbecillus "weak, feeble," a word of uncertain origin.
The Latin word traditionally is said to mean "unsupported" or "without a walking stick" (Juvenal: imbecillis: quasi sine baculo), from assimilated form of in- "not, opposite of" + baculum "a stick" (see bacillus), but Century Dictionary finds that "improbable" and de Vaan finds it "very far-fetched" and adds "it seems to me that exactly the persons who can walk without a support are the stronger ones." There also are phonological objections.
Sense shifted to "mentally weak or incapable" from mid-18c. (compare frail, which in provincial English also could mean "mentally weak"). As a noun, "feeble-minded person," it is attested from 1802. Traditionally an adult with a mental age of roughly 6 to 9 (above an idiot but beneath a moron).