vacillation (n.)youdaoicibaDictYouDict[vacillation 词源字典]
c. 1400, "hesitation, uncertainty," from Latin vacillationem (nominative vacillatio) "a reeling, wavering," noun of action from past participle stem of vacillare "sway to and fro, waver, hesitate, be untrustworthy," of uncertain origin. Originally in reference to opinion or conduct; literal sense is recorded from 1630s.[vacillation etymology, vacillation origin, 英语词源]