hesitation (n.)

c. 1400, from Old French hesitacion or directly from Latin haesitationem (nominative haesitatio) "a hesitation, stammering," figuratively "irresolution, uncertainty," noun of action from past participle stem of haesitare "stick fast, remain fixed; stammer in speech," figuratively "hesitate, be irresolute, be at a loss, be undecided," frequentative of haerere (past participle haesus, first person perfect indicative haesi) "to adhere, stick, cling."

This is said by Watkins to be from PIE root *ghais- "to adhere, hesitate" (source also of Lithuanian gaišti "to delay, tarry, be slow"), but some linguists reject the proposed connection; de Vaan offers no etymology.