Yours, Etc.: Origins and Uses of 8 Sign-Offs
1640s, "unsafe," from Medieval Latin insecurus, from in- "not" (see in- (1)) + Latin securus (see secure). Psychological sense dates from 1935; insecurity in this sense dates from 1917. Related: Insecurely.
insecure in·se·cure (ĭn'sĭ-kyur')adj.
Lacking emotional stability; not well-adjusted.
Lacking self-confidence; plagued by anxiety.