Executer with the "er" suffix is the actual man doing the action. as in giver or skier or promiser. Executor with the "or" is the indication of the agent "acting" for the party of interest. as in donor or promisor or trustor. Both words are in Webster's 1828 online dictionary and the definitions clarify this distinction. This role of the suffix to change the word (root) meaning seems to be ...
