origin of the x-ray

the x-ray was first called the roentgen ray--in honor of the scientist who discovered it. but he preferred to call it x-ray, because x is the algebraic symbol of the unknown, and at that time he didn't understand the nature of what it was he had discovered.

i found this wonderful photo here, by darkyard. it is one in a small series of naughty x-rays, and if you're interested they do get a bit naughtier.