Monks had a lot of influence on spelling. In French, they abbreviated the "ls" at the end of some words to "x", thus "animals" becoming "animax" (later "animaux", as others added a "u" to make the spelling fit the pronunciation better).

'Connexion' is the one I have come across most frequently, and most of that was when an old colleague leant me a book he got as a child about engineering feats from the late 1800s and early 1900s (up to about 1940). They still used the 'x' instead of 'ct' when writing it, though it was British.

connexion reflects the Latin etymology -- it comes from the Latin word cōnexiō (junction)

This is super interesting? Any pointers to good articles about this?

Many spellings can be traced back to specific print shops. "would could should", for example.