#MeToo is about sexual assault/rape/sexual harassment/molestation etc. rather than differentiation of gender terms.
Quite right, Birdy. I stand corrected.
I don't have any evidence, but I do suspect that the words
alumnus and
alumni, while far from being unknown in UK, are much more common in the US.
For example, I would never describe myself as an
alumnus of St X's school or of the University of Y.
When I was teaching in UK the usual terms were OBs (old boys), OGs (old girls) or, more commonly, FPs (former pupils) when referring to people who had attended a school and
graduate for someone who had successfully completed a course of study at a college or university.
Alumnus would have sounded a bit formal, possibly even a little pretentious.
Alumna was very rare indeed.