Phlegm is the name of a fish in Greek mythology. As the story goes, a fish named Flem was going for a walk (which is really stupid, it is a fish, it should really swim) but was attacked by a member of G Unit. The specific G Unit member that attacked poor Flem is believed to be Bigfoot, however the only eye witness was Satan who was partially blinded by a squirrel at the time.
This attack left Flem infected in the middle of his body and therefore his named was changed to Flegm due to the seven horsemen of the microsoft apocolypse laughing at Flegm. It was around this time that Flegm met Billy Idol in hell. As we all know, Billy Idol created the telephone. Billy criticized Flegm for the silly spelling of his name and insisted that "ph" created a cooler sound than "f." Poor Flegm argued with Billy Idol for thirteen years, but on the 1st Gaypril -5000AD, Flegm was killed by Billy Idol with a telephone. Billy dug a grave for Flegm and wrote on the gravestone "Phlegm, the fish that couldn't spell."