Where does “прямо-” come from?

прямо- (Russian) comes from Russian прямо́й, from Old East Slavic прѧмъ, from Proto-Slavic pręmъ, from Proto-Slavic prěmъ — straight?, correct?, direct?.

Ancestry of “прямо-”, step by step

прямо- traces back through two separate lines of ancestry.

via Russian прямо́й

StepLanguageWordMeaning
1Russianпрямо́йstraight, direct
2Old East Slavicпрѧмъ
3Proto-Slavicpręmъstraight?, correct?, direct?
4Proto-Slavicprěmъstraight?, correct?, direct?

via Ukrainian прями́й

StepLanguageWordMeaning
1Ukrainianпрями́йright, direct, straight
Every word from Proto-Slavic prěmъEvery word from Proto-Slavic pręmъEvery word from Old East Slavic прѧмъ