There's an account of the British ae/oe and American "e" spellings (as in diarrh(o)ea, f(a)eces, and other fun words) on wikipedia.
What I'm wondering is why, even in British English, pedagogue/pedagogy etc. lose the "a", despite coming from the same "paid-" root as e.g. paediatrics.
I've checked the OED, and the ped- spelling seems to consistently predate paed- - as in e.g. Pedocracy (1647) and Paedocracy (2000). Here, for those who have access.
So, can anyone:
- shed any light as to why/when/how British English regained that lost vowel in all other ae/oe words than pedagog-?
- and/or suggest other words with similar behaviour in British English?
UPDATE: to clarify, the question put more technically is: what is the basis for some words containing what were originally Ancient Greek diphthongs oi/ai coming into the language informally referred to as British English written with just an "e" and not ae/oe?