我聽過有第二個講法,
現今好多俚語其實黎自二戰, 而COPY that, 據聞都係個個時候出現,
同一年代既俚語有 :
Roger that 收到 (下面quote解釋)
G.I.Joe 美國大兵 (Government issue Joe),
Joe 係當時係公廁名, 所以就係指, 你只係政府公發既一個大兵, 女既會叫 G.I. jane ( Merry jane = 大麻就應該唔關事)
Roger" originated from the radio alphabet, which begins, Able Baker Charlie Dog...etc and was the official radio alphabet of the US Navy prior to 1954. "Roger" is word that coincides with the letter "R". In radio talk, the "R" stands for "received".... So when someone confirms that they received the message, they would reply with "Roger"
"Copy" is the same thing... however, there is no official reason to use it. Copy is not apart of any "official" radio language. If nothing else, it is nothing more than radio slang for "copy that". This term was introduced by truckers operating on Citizen Band radios. Truckers often came up with their own terms and verbage to use on the radio, most often so that law enforcement couldn't understand their messages.
As a little side note, you will often hear the term "Wilco" in conjunction with "Roger"... "Roger Wilco".... For what its worth, "Wilco" is short for "Will Comply". When you say Roger Wilco, you are saying, I receved your message and I will comply.