Language / Children's Songs in Polish [66]

Hello. My great grandmother use to sing a song to me while clapping our hands like patty cake. I always thought the first words were cushy but after researching it seems that the word might actually be kosi. So, it started off sounding like kosi kosi kosanki. Does anyone have any idea what this could have been? I would love to teach it to my children but I don't want to teach them the wrong words. I can only pronounce the words the way I remember hearing them.