How was the Nazi Salute founded?

The Nazi Salute has two origins, both of which are disputed at times.

Number one: The most plausible theory:

Adolf Hitler moDELLed the Nazi Salute after ancient Roman soldiers, who would jut their arms forward in the same way as a salute to their superiors.

Number two: The other theory:

Hitler took the fascist arm raise from Benito Mussolini (Commandant of the Italian Army), who invented it because he had a fear of handshaking.