The Tocharian word empreṃ 'truth' is often marked as being of unknown etymology. I cannot find a lot of commentary on it except from that it could be a middle Iranian word meaning 'confidence'.
So, my first question is if there's any good proposal on a PIE root for this word?
My second question is more like checking the validity of my idea that the word might derive from PIE *per- 'cross, pass through'. The reason I am suspecting this is because Greek has πεῖρα ‘test, research, experience’ deriving from the same root. If that semantic development occurred in Greek, then truth, test and experience are very relevant to each other.