"Rodger" was the original meaning of the letter "R" in the phonetic alphabet. First making its appearance around 1938, it was used by the military in place of the "received." It meant that the transmission sent, whether by radio or Morse code, had been received by whom it was sent to. The military later replaced it in 1954 with the current meaning.
Contrary to popular belief, it did not mean that the message would be complied with. In today’s world, the military still acknowledges the receipt of a command or orders by replying with "Roger," "Roger, returning to base," or however relevant. In the phonetic alphabet today, the term "Roger" has been replaced by the term "Romeo" when used for the meaning of the letter "R." The misconception of Roger standing for an acknowledgement and following through on an order has been the cause of numerous accidents in aviation. In Geneva, Switzerland, land flights DLH3703, ATR42-500, and KLM1931, with a Boeing 737-300, crashed into each other due to a misuse of the word "Roger," causing KLM1931 to hold on the runway and DLH3703 to crash into it.
Today, the term "Roger" is still used by pilots and ATC alike to reduce actual time on the radio, but it is important to note the difference in meaning between "Roger" and "Wilco." Wilco means that the receiver of the transmission will comply with the order. This is why the term "Roger, Wilco" is commonly heard in the military. "Roger, Wilco" formally means, "I received the transmission and will comply with the order."