[porges]

That's mostly because Encyclopædia Britannica is styled that way.

[fifnir]

Which is because the word was made by french based on the greek εγκύκλιος παιδεία

εν-κύκλος (in circle) --> εγκύκλιος παιδεία (education)

The core, generalized education one should have.

Words like paedagogic etc are also spelled like this in english (uk) because the language maintains the historic spelling