
So I looked into this a bit and…
it appears to be based on whether a word is using Latin or Greek as its etymological basis, for words pertaining to feet.
In Latin… it is ped-… but in Greek… it is pod-.
… And, you are correct, English has a mish mash of both.
But also, a lot of English words referring to children use the Greek derived ped- or pedo- to refer to… children.
…Which is why in British English, the spelling ‘paed-’ is used, to minimize this confusion.
But us clever Americans dropped that, rofl.


Well, if you try not to think about it too hard, you may fall right about wherever Spike does:
https://youtube.com/watch?v=LO0MRVjcY4E