Co-ed frats aren't just "nowadays." I was one of a class of two first female members of the MSU chapter of AKPsi back in the day.

AKPsi is a "professional" frat in that it is for business majors, but it is (at least, our chapter was) very social, in that it had a residential house and the usual menu of parties, intermural teams and such.

It was, and is, called a frat because it started as a frat.