Why use the word "copy" in "do you copy that"?
I notice "do you copy that?" is used in movies to ask for confirmation in telephone/interphone conversation.
I only know copy means make things duplicated, so why use it in "do you copy that"? Is there a history about it?
This comes from military, amateur and CB radio communication
"Do you copy?" or "Copy that!" is likely from when a message had to be written down to be shown to a superior officer
http://en.wikipedia.org/wiki/Voice_procedure
Some words with specialized meanings are used in radio communication throughout the English-speaking world, and in international radio communications, where English is the lingua franca.
Affirmative — Yes
Negative — No
Reading you Five / Loud and clear — I understand what you say 5x5.
Over — I have finished talking and I am listening for your reply. Short for "Over to you."
Out — I have finished talking to you and do not expect a reply.
Clear — I have finished talking to you and will be shutting my radio off.
Roger — Information received/understood.
Copy — Mostly used to acknowledge received information. [May also mean Repeat back to me the information I just gave you. ed.]
Wilco — Will comply (after receiving new directions).
Go ahead or Send your traffic — Send your transmission.
Say again — Please repeat your last message (Repeat is not used as it is a specific command when calling for artillery fire)
Break — Signals a pause during a long transmission to open the channel for other transmissions, especially for allowing any potential emergency traffic to get through.
Break-Break — Signals to all listeners on the frequency, the message to follow is priority.
http://www.dyerlabs.com/communications/procedural_codes.html
Copy probably originally referred to writing or typing a received message, but now has is essentially the same as 'Reading you ...'.
This phrase originated with Morse Code. You can make a perfect copy of the sounds you hear onto a sheet of paper.
The phrase undoubtedly came into popular use from Amateur (ham) Radio users who moved into CB radio. Amateur Radio users discuss copying traffic as part of their hobby. http://www.arrl.org/appendix-b-nts-methods-and-practices-guidelines
Amateur radio has a list of short-hand symbols that are used to quickly transfer information through Morse Code (and later were used over-the-air). One of the most popular is QSL which means either Do you copy or I copy. Amateur Radio users first started sending QSL cards to acknowledge successful contacts around 1920.
http://en.wikipedia.org/wiki/Morse_code
Two years later, I find another wrinkle in this tapestry.
http://en.wikipedia.org/wiki/Procedure_word mentions that Copy has a specifically different use from Roger in Maritime VHF. Copy is used to mean "I heard that as well" when a message between two stations includes information that has some sort of importance to another station. For example, Boat A tells Boat B that there's debris in the water and gives GPS coordinates. Boat B responds "Roger." Boat C breaks in and responds "Copy that."
This explanation of the distinction seems to make sense. It also makes sense that these two meanings would run together over time, especially in more informal radio traffic.