[scrabblehack]

Dux, Rex, Lux?

Maybe you mean at the beginning of a word?

That’s rare, but it does happen.
xiphias = “swordfish.” (in Pliny).

[Larry Lucido]

I was being a bit facetious, referring to the tendency of some to refer to folks (folx?) as Latinx (sic) instead of Latins, Latinos or Latinas. A bunch of minxes, if you ask me.

[Fiji Hill]

Dux, Rex, Lux?

Also ex post facto, ex libris, praxis, etc.