Got more than one site with it too, including definitions.
Of course your son need never know why your calling your dominant that, it could easily be taken as a term of endearment. In any event I think it's romantic.
Not that its nessesary to have any special reference or titular distinction between partners. I am sure you both know the score regardless of which title if any you use, in private or otherwise.
Hopefully the kids who are big enough to google don't know how to spell, Lol! No I agree about the title not being required , except it makes Him happy and helped me remember what was lost in a house full of teenagers.