Where does “Mc” come from?

Mc (Translingual) comes from English moscovium, from English -ium, from Latin -um, from Proto-Italic *-om, from Proto-Indo-European *-oHom.

Ancestry of “Mc”, step by step

StepLanguageWordMeaning
1EnglishmoscoviumThe chemical element with atomic number 115
2English-ium1997, Bryan Pfaffenberger, "Official Microsoft...
3Latin-umnominative neuter singular of -us; accusative...
4Proto-Italic*-om—
5Proto-Indo-European*-oHom—
Every word from Proto-Indo-European *-oHom →Every word from English -ium →Every word from Latin -um →