Not sure Chris — RDF perhaps Resting Dick/Douche Face? Neither one really seems to fit exactly though. If you find one I’d be glad to know. Possibly the male form is more socially acceptable (the generic scowl)? But too true, it does keep the world at bay.
I believe it’s a bit of both. Introversion, different interests, and not fitting in all contribute to our discomfort and exacerbate the “face”, which, in turn, scares away even more potential contact. Vicious circle.