I'd argue "per annum" or p.a. isn't a foreign term and just standard English. English is full of Latin words, transparent, opaque, foreign, those are all words of Latin origin.
> I'd argue "per annum" or p.a. isn't a foreign term and just standard English.
Did you notice that a fluent English speaker had to ask what "p.a." meant? Do you think that would have happened if it had been written "per year" instead?