aggie (n.1)
"college student studying agriculture," by 1880, American English college slang, from agriculture + -ie.
aggie (n.2)
type of toy marble, by 1905, American English, colloquial shortening of agate (q.v.).
Excited groups gather about rude circles scratched in the mud, and there is talk of "pureys," and "reals," and "aggies," and "commies," and "fen dubs!" There is a rich click about the bulging pockets of the boys, and every so often in school time something drops on the floor and rolls noisily across the room. When Miss Daniels asks: "Who did that?" the boys all look so astonished. Who did what pray tell? ["McClure's Magazine," May 1905]