If only she could figure out why she got these regular, periodic, euphemistically described pains! What could they possibly be? Perhaps they meant "periodic" to mean "period," but given the horror they had for frank descriptions of female troubles, I doubt it. Still, it's close, so there must have been some arguments.

How should we describe menstrual pains?

They're recurring and regular times, right? Call 'em . . .periodic.

But that's pretty close to period.

Get your mind out of the gutter, Johnson.