[quote=Sole]
It's very common, whether you've heard of it or not. That's like saying you didn't break a law because you didn't know it existed.
It's also dependant on the organization. Some organizations do it, others do not and will add the two T's to include transsexual and transgender.
[/quote]

Or: it's not very common, whether you've heard of it or not. That's like saying bagged milk is a household staple just because you've heard of it before.