another common name is "fireworm" ... touch one and you'll know why ;-)
Technically speaking not all bristleworms are fireworms, but all fireworms are bristleworms.
Bristleworm is the common name referring to the class Polychaete. There are roughly 10,000 different species.
During my years of farming coral I had to remove these bristles from my hands on a weekly basis. Very few of them ever caused me any discomfort.