Where does “u” come from?

u (Slovak) comes from Proto-Slavic u, from Proto-Balto-Slavic au, from Proto-Indo-European h₂ew, from Proto-Indo-European ǵʰe — Postpositional intensifying particle: indeed, at any rate, in fact.

Ancestry of “u”, step by step

StepLanguageWordMeaning
1Proto-Slavicuat, near, by
2Proto-Balto-Slavicau—
3Proto-Indo-Europeanh₂ewaway from, off; again
4Proto-Indo-EuropeanǵʰePostpositional intensifying particle: indeed, at any rate, in fact
Every word from Proto-Indo-European ǵʰe →Every word from Proto-Indo-European h₂ew →Every word from Proto-Balto-Slavic au →