It seems like an easy question doesn't it? After all, most everyone knows that Oregon State University was Oregon Agricultural College before 1927... But that's a mouthful: OR-E-GUN AG-RI-CUL-TUR-AL COL-LEGE — 10 syllables, versus the 4 syllables of "Oregon State"?
Presented with bloated names, people tend to economize, to shorten. Just calling the school "OAC" would work, in the same way that USC and UCLA are the common names of schools with bloated full names today. There is no doubt that this was the way that most Beaver sports fans handled the dilemma back in the day.
But guess what? There was another way that Oregon Agricultural College was differentiated from the University of Oregon before 1927...
Yep, OAC proudly touted themselves as "Oregon Aggies" before there was such a thing as Oregon State, as this 1924 football gameday program documents.
It's also interesting that Idaho and Montana were part of the old Pacific Coast Conference before getting booted in favor of UCLA to form the Pacific-8 Conference.
Trivia everywhere today...