いたずら
いたずら · itazura · JLPT N3 · noun
trick
🃏 From 徒ら itazura, meaning idle or futile: mischief done for no real purpose
いたずら first meant pointless or in vain, and いたずらに still means in vain. The usual spelling 悪戯 is ateji: bad (悪) + play (戯), so a prank is bad play with no real goal.