Copy that is a military and radio term, used synonymously to understood.
We may often hear it in movies and series, whenever officials are talking over a radio intercom.
Copy that comes from the 19th century, when the medium of choice in communication was Morse code, where you are able to make a perfect copy of the sounds you receive.
This technology was still utilized later by amateur radios, even over the air.
The phrase was known by generations and generations of people, who had interacted with radio communication systems, either during wartimes, or just as a hobby radio user.
Movies also contributed to the wider recognition of the phrase, as nearly every military motion picture is featuring the term.
Urban Dictionary has but two definitions on the phrase, one coming from 2005, while the other one was written in 2016.
While you probably won’t encounter copy that in a live conversation with someone, you most likely already heard and seen it in one form or another.
- Urban Dictionary – Copy that