Word Origin & History
late 13c., from L. senior "older," comparative of senex (gen. senis) "old," from PIE base *sen- (see senile
). Original use in English was as addition to a personal name when father and son had the same name; meaning "higher in rank, longer in service" first recorded 1510s.
The L. word yielded titles of respect in many languages, cf. Fr. sire, Sp. señor, It. signor. Noun sense of "fourth-year student" is from 1741, from earlier general sense of "advanced student" (1610s). Seniority "priority on office or service" is from mid-15c. Senior citizen first recorded 1938, Amer.Eng.