Potato?

If GH can stand for P as in Hiccough
If OUGH stands for O as in Dough
If PHTH stands for T as in Phthisis
If EIGH stands for A as in Neighbour
If TTE stands for T as in Gazette
If EAU stands for O as in Plateau

Then the right way to spell POTATO should be: GHOUGHPHTHEIGHTTEEAU