There is also another interesting unwritten rule of the English language at play here. The rule goes like this:

In a series of words which differ only (or mostly) by the vowel used, the order should be e, i, a, o

- tic tac toe

- flim flam

- ding dong

- king kong

If you doubt it, try saying the opposite and hear how odd it sounds: The clock went 'Tock Tick'