The Focke-Wulf Fw 61 is often considered the first practical, functional helicopter, first flown in 1936.
Guys, this isn't hard to look up.
ok i actually did go and look it up now. Of all the european languages, only 5 other languages use x-ray to describe the radiation type. So you are definitely wrong.
btw the english wiki article say x-rays, or röntgen rays. So not only would many people from other countries get what you mean, it is actually correct in english aswell.