precession (n.)youdaoicibaDictYouDict[precession 词源字典]
1590s, from Late Latin praecissionem (nominative praecissio) "a coming before," from past participle stem of Latin praecedere "to go before" (see precede). Originally used in reference to calculations of the equinoxes, which come slightly earlier each year.[precession etymology, precession origin, 英语词源]