1610s, "lack of ability, powerlessness," from French incapacité (16c.), from Medieval Latin incapacitatem (nominative incapacitas), from Late Latin incapax (genitive incapacis) "incapable," from in- "not" (see in- (1)) + Latin capax "capable," literally "able to hold much," from capere "to take," from PIE root *kap- "to grasp." As a legal term (1640s), "lack of qualification," referring to inability to take, receive, or deal with in some way.
