clipped from: web.archive.org   
“roger” to acknowledge receipt of a message or instructions. “Roger” at one time was the phonetic designation for the letter R, which in turn stood for “received.”

From a safety perspective, it makes sense to use standardized language, particularly when dealing with international operations. An American pilot may not understand German, but they both understand aviation terminology.

In the military's phonetic alphabet, "roger" didn't become the designation for R until 1927

In 1957 "roger" was replaced by "romeo," the current designation, but by then "roger" = "received" was so entrenched that the brass knew better than to try and change it.

“roger, roger” in Phantom Menace

sly (OK, not that sly) reference to Airplane (1980)

such lines as:

Captain Oveur (Peter Graves): Roger, Roger. What's our vector, Victor?


pilot who invokes our friend Roger Wilco is saying “I understand you, and will follow your instructions,” only cooler and shorter.