We gave our first daughter two middle names, after both our mothers. So she was Fn
Beatrice Mary. MIL's name was
Bertha Maria, but we preferred
Mary, and we are probably the least religious people we know. So, I'd assume that
Mary was a family name - just about every family has a
Mary ancestor somewhere, if not several - or else that they just liked it, same as we did.
Mary OliviaMary LilianMary EmiliaMary Lucinda