[ttt0]

"Referring to the origin [...] of such groups" might be it, but yeah, "common and distinctive culture, religion, language, or the like" alone doesn't make an ethnicity. I suspect the existence of ethnic groups will be denied too at some point, or labelled as "offensive".

[exporectomy]

Oh yes, I overlooked that. I would have thought it would be the only meaning, or at least the first one.