From Proto-Germanic*rēswô(“counsellor”), from Proto-Germanic*raisa-, *raþja-, *raid-a-(“account, explanation”), from Proto-Germanic*rē-, *rai-, *rī-(“to count, talk”), from Proto-Indo-European*(a)rēy-, *rei-(“to regulate, reason, count”). Cognate with Old Norseræsir(“leader, chief, king, prince”), Old Englishrǣswan(“to consider, conjecture”).