Aside from being the name of a biblical character, "blastus" is another term designating a type of fart. A very large amount of intestinal gas is expelled at considerable force. As the flattus is violently expelled through the anus, the high amplitude oscillation of the sphincter results in a great, explosive, low tone of frightful volume. The term may also be applied as a proper noun as necessary.
Grotee let loose (with a "blastus") and it shook the walls. That's why they call him Blastus.