Limey comes from the fact that when your ancestors crossed over from the U.K They had to eat limes to prevent jaundice, hence limeys.
The word POSH comes from these times also. Portside Out and Starboard side In, for travel on a boat,
I do not feel they are offensive terms ' forg' etc as there is much worse you can call them.
Oh yes the frogs helped liberate your country from who ? the native Americans.