ko (Slovene) comes from Proto-Slavic jako, from Proto-Slavic jakъ, from Proto-Slavic jь, from Proto-Balto-Slavic iś, from Old Polish ić, from Proto-Slavic jьti, from Proto-Balto-Slavic eitei, from Proto-Indo-European h₁éyti — to go.
ko (Slovene): when; Alternative form of kot