Hi
It is the anglo/francophone-ization of a geographical name based on who was in charge of the area at the time.
I have read military accounts from pre and post WW1 referring to that what is now
Saint-Jean-sur-Richelieu, Quebec as
Saint or
St John or
Johns due to the French then ultimately British Garrison there since 1666. Only really after WW2 did it most often be referred to as Saint Jean or Saint-Jean-sur......etc.
I believe the WW1 22nd Battalion was raised in Fort Saint John (Fort Saint Jean).
regards
Darrell