Where does “stepbairn” come from?
stepbairn (English) comes from Middle English stepbarn, from Old English stēopbearn, from Proto-West Germanic *steupabarn, from Proto-Germanic steupabarną, from Proto-Germanic steupa-, from Proto-Indo-European (s)tewp-, from Proto-Indo-European (s)tew- — to push, to hit.
stepbairn (English): A stepchild
Ancestry of “stepbairn”, step by step