So, to explain the rule: if you have three words, then the vowel order has to be I, A, O. In the case of two words, the first is almost always an I and the second is either an A or O. For example, Mish-mash, chit-chat, dilly-dally, tip-top, hip-hop, flip-flop, tic tac toe, sing-song, ding-dong, King-Kong, ping pong.
According to the secret rules of English it should be that way round.