They are called fluorescent lamps because the white powder (a blend of phosphors) actually fluoresces in response to the ultraviolet radiation on the inside of the tube. Wikipedia, the free encyclopedia, has an excellent discussion of fluorescent lamps including the history and all technical aspects. Fluorescent lamps on Wikipedia.
What are Ultraviolet (UV) lamps?
These are special fluorescent tubes/lamps/bulbs that emit ultraviolet radiation. The low pressure mercury vapor tubes that emit UV C radiation do not have any phosphor in the tube, the mercury vapor produces the UV C radiation. For low, medium, and high pressure mercury vapor tubes that emit UV B, UV A, or a blend of UV A and UV B, the inside of the tube is coated with a phosphor or a blend of phosphors. Ultraviolet phosphors are materials that absorb the UV C and re-emit the energy as UV A or UV B radiation.