It's a completely fabricated neologism/portmanteau and more importantly an entirely unnecessary one at that.
It's not a common word and not one which would typically be used in everyday life but as neologisms go it's quite good.
It has a nice precise meaning and no emotional baggage and simply describes the most usual version of "something"-gendered. It's a bit like heterosexual in that regard.
I would be slightly wary about using it as often it's used in Atheism+ as I'm not sure how much of a barrier it could potentially put up between transgendered and cisgendered. Especially for those transgendered who have no desire to get involved in the sexual politics.
But I'm wading into deep waters and flailing about blindly here, so I'll shut up.