declination (n.)youdaoicibaDictYouDict[declination 词源字典]
late 14c. as a term in astronomy, from Old French declinacion (Modern French déclinaison), from Latin declinationem (nominative declinatio), noun of action from past participle stem of declinare (see decline (v.)). It took on various other senses 15c.-17c., most now obsolete.[declination etymology, declination origin, 英语词源]