climbing plant, Old English ifig, from West Germanic *ibakhs (source also of Middle Low German iflof, Dutch eiloof, Old High German ebahewi, German Efeu), a word of unknown origin; the second element in the Old High German word might be heu "hay."
Ivy bush as a sign of a tavern where wine is served is attested from mid-15c. (the ivy being sacred to Bacchus). Ivy League, inspired by the image of old, ivy-mantled walls, dates to 1935, originally in reference to a conference of football teams agreeing to organize teams and play games by set rules; it consists of Brown, Columbia, Cornell, Dartmouth, Harvard, Pennsylvania, Princeton, and Yale.
Incidentally, "Ivy League" is a poor name; it suggests that athletic morality is concentrated in a few very old colleges. Obviously, membership should be determined not by the amount of ivy on an institution's walls, but by its willingness to adopt and follow certain fundamental principles of education and sport. [Princeton Alumni Weekly, Dec. 6, 1935]