Where does “посторонний” come from?

посторонний (Russian) comes from Russian ПО, from Old East Slavic по, from Proto-Slavic po, from Proto-Indo-European h₂pó, from Proto-Indo-European h₂epo — from, off, back; off, away; off, from.

посторонний (Russian): strange, outside, foreign

Definitions

  1. strange, outside, foreign

Ancestry of “посторонний”, step by step

посторонний traces back through two separate lines of ancestry.

via Russian ПО

StepLanguageWordMeaning
1RussianПОsoftware
2Old East Slavicпоon, along, by
3Proto-Slavicpoafter; by; at
4Proto-Indo-Europeanh₂póoff, away
5Proto-Indo-Europeanh₂epofrom, off, back; off, away; off, from

via Russian сторона́

StepLanguageWordMeaning
1Russianсторона́side, hand, party
2Proto-Slavicstornàside, land
Every word from Proto-Indo-European h₂epoEvery word from Proto-Indo-European h₂póEvery word from Proto-Slavic po
посторонний — Etymology, Origin & Word History | Etymology Explorer