imbecility

1533, "weakness, feebleness, impotence," from L. imbecillitatem (nom. imbecillitas) "weakness, feebleness," from imbecillus "weak, feeble," traditionally said to mean "unsupported" (quasi sine baculo), from in- "not" + baculum "a stick." "Weakness in mind" (as opposed to body) was a secondary sense in L. but was not attested in Eng. until 1624. Imbecile is first recorded 1549 as imbecille (adj.) "weak, feeble" (especially in reference to body), from M.Fr. imbecile, from L. imbecillus. As a noun, it is attested from 1802. Traditionally one with a mental age of roughly 6 to 9 (ahead of an idiot but beneath a moron).