Yes, white phos. From the initials 'W P'
It isn't white itself however, thats traces of phosphorus oxides, perhaps in some cases polymeric phosphines, but mostly oxides like P2O5 (most vicious bugger of a dehydrating agent you will ever be likely to meet....it'll dehydrate sulfuric acid to sulfur trioxide, or even perchloric acid to its anhydride, although I've never tried the latter rxn)
Theres some pics on sciencemadness.org of a guys WP that he purified with first hot H2SO4, then dichromate solution, to get it so pure it was no longer white or yellowish, but CLEAR...like....glass clear. Absolutely amazing photos, well worth checking out, its a recent thread on purification of WP and care of burns. Fucking had me going, that I have to try. It turns color really quickly back again apparently, but the pics were beautiful examples.
Had a nasty accident with it as a lil'un, distilling the stuff.
Got a TINY bit on me, just the merest little speck and the burn that resulted was not only painful, but left neurologic issues behind with motor control of the burnt arm for quite some time after, mainly tremor and severe muscle weakness.
Hurt worse than a regular burn too.
No brainer really. Name wise. Stuff makes for a fantastic display of phosphorescence, and burns like a fucking bastard, of course, being pyrophoric, it takes little encouragement to do it so makes a pretty nasty incendiary agent also, hence use in warfare.