Why do people say "Roger that"?

[CharlottetlmmmmtMOZZA]

I know it means "I understand" or "I copy that". But what's the origin of "Roger"?

 

[Sarah]

roger was a military term used by pilots or radiomen inthe army so they could confirm to their commanding officer that they got their orders and understood them

 

[Sarah]

roger was a military term used by pilots or radiomen inthe army so they could confirm to their commanding officer that they got their orders and understood them