I always heard them saying ' roger' which i think means 'Got it' or 'yes sir'. However,I wanna ask..who started saying this and why must they say roger instead of any other names.. ?
Roger=R in the phonetic alphabet, it was used over radios during war time for brevity, as you had to be very careful and quick as possible when sending messages over the radio, as the enemy were always likely to tune in.
So yes as you say it means 'Got it', 'Received clearly', etc.
Roger, in Military radio procedure means transmission received it is usually followed by the word "out" meaning end of conversation. Standard radio procedure makes it possible for different branches of the military to communicate effectively, clearly and concisely over the radio. A transmission using proper military procedure insures that parties do not talk at the same time. An example: headquarters call sign - Druid, patrol call sign - Druid Oscar ( the headquarters call sign precedes the patrol call sign when conversing with units not assigned to Druid. Oscar represents the letter "O".
The transmission: Druid Oscar this is Druid, over.
Druid Oscar, over (connection established)
Druid: Proceed to meet Druid November at, I Shackel, Alpha, November, Sierra, Foxtrot, Oscar, x-ray copy, over.
Druid this is Oscar I copy meet with November Shackel Alpha, November, Sierra, Foxtrot, Oscar, x-ray wilco over,
This is Druid Roger Out.
Druid this is Druid November Roger your last,Out.
Shackel is a code changed daily where the letter represents a number, in this instance, a map coordinate. A, N, S, F, O, X two letters could equal the same number 9 3 3 4 0 6.
I just want to repeat that "roger" is not an acceptable answer to a yes/no question. "Roger" means that you received the previous transmission. The only acceptable answers to a yes/no question are "affirmative" and "negative".
"Roger" is also not a particularly useful response to a suggestion if the person asking needs to know if you will take the suggestion or not. That is because it doesn't communicate whether you will take the suggestion or not.
For example, suppose two people are supposed to meet at point A. One of them says "recommend we meet at point B". The other says "roger". Now where are they meeting?
The R that Roger is substituting for stands for received, indicating that a radio message has been received and understood. The use of radio-alphabet terms to stand for other words is common in the military; roger is a well-known example, and another example is Charlie referring to Viet Cong troops, which comes from Victor Charlie, a radio-alphabet spelling of VC for Viet Cong.
"Roger" means "I have received all of the last transmission" in both military- and civilian aviation radio communications. This usage comes from the initial R of received: R was called Roger in then-current radio alphabets such as the Joint Army/Navy Phonetic Alphabet. It is also often shortened in writing to "rgr". R is Romeo in the modern NATO phonetic alphabet. Contrary to popular belief, Roger does not mean or imply "I will comply". That distinction goes to the contraction wilco (from, "will comply"), which is used exclusively if the speaker intends to say "received and will comply."
It started, actually, with ham radio operators decades ago - it is easier to acknowledge receipt of a message in Morse code by sending a series of three letters R - than it is to send "I copy all of the foregoing message". When U.S. participation in World War One began, the government ordered all ham radio stations off the air and a number of hams enlisted - as signalmen. They continued to use their radio skills, including the "Q-code" when transmitting messages for the Armed Services. When more and more radio operators used voice communications instead of Morse code, they adopted their own slang. The Morse sign R R R became "Roger" or "Roger that". Yes, it was both utilitarian and somewhat adolescent attitude. Hey, it's a guy thing...
dahdidah dahdahdit dididahdahdah dahdidit didit <--- my ham radio call sign in Morse code...