Enter Sadie Stein on this The Paris Review article:
Now, there’s a term you don’t hear anymore! The “college widow”! Once a byword for a predatory vamp, the college widow is an extinct American species.
I’ve read various definitions of the college-widow meme, which appears regularly in books and films from the first half of the twentieth century, and was de rigueur in any discussion of campus life. In some cases, these characters were portrayed as literal widows—young women who’d known the marriage bed and were hungry for young collegiate flesh. But more often, the term seems to have applied to a townie—or grad; at any rate, a woman hanging around—who dated men in successive senior classes, and were subsequently “widowed” with each passing graduation.
The rest of the article is worth reading, too, especially this pull from the now-defunct blog Paper Pop:
Filmmakers had to assure us that our heroes were healthy, red-blooded American men, who would never resort to all that Brideshead Revisited stuff that was rumored to go on at many an all-male campus. Obviously in the 1910s–1940s (the heyday of this trope), prostitution couldn’t be depicted on screen, so our protagonists couldn’t get their kicks that way. Once the Hays Code came into effect, adulterers must be punished. And for a hero to seduce an unmarried young woman would be caddish. So the college widow served as an effective outlet for all of our heroes’ wants and needs (and those of the writer): it proved the protagonist was straight, sexually desirous and desirable, and yet still a gentleman. Of course, the trope began to be played for laughs even more often than it was played straight, in movies like Horse Feathers [Marx Brothers' parody of this meme]. With the rise of co-education and the fall of the production code, the college widow found herself expelled from campus in favor of flirtatious co-eds.
While browsing the Etymology Dictionary, as one does, at the end of the entry for college comes the note "College-widow is attested by 1878." What the heck is a college-widow?
Enter Sadie Stein on this The Paris Review article: The rest of the article is worth reading, too, especially this pull from the now-defunct blog Paper Pop: I should've known sexism was involved.