diffidence (n.)

c. 1400, from Latin diffidentia "mistrust, distrust, want of confidence," from diffidere "to mistrust, lack confidence," from dis- "away" (see dis-) + fidere "to trust" (from PIE root *bheidh- "to trust, confide, persuade"). Modern sense is of "distrusting oneself" (1650s). The original sense was the opposite of confidence.

Diffidence is a defect: it is an undue distrust of self, with fear of being censured for failure, tending to unfit one for duty. [Century Dictionary]