alumnus (n.)

"pupil or graduate of a school," 1640s, from Latin alumnus "a pupil," literally "foster son," vestigial present passive participle of alere "to suckle, nourish," from PIE root *al- (2) "to grow, nourish." With ending akin to Greek -omenos. Plural is alumni. The fem. form is alumna (1882), plural alumnae.