A pissant, also seen as piss-ant and piss ant, is one or the other of two specific types of ant. The word can also refer to an inconsequential, irrelevant, or worthless person, especially one who is irritating or contemptible out of proportion to his significance. Its origin is with pismire, a 14th-century word for ant. 
The original pissant is any of a certain group of large ant species, commonly called wood ants, that make mounded nests in British and European forests. The pissant name arises from the urine-like odor produced by their nesting material—pine straw and pine needles—and the formic acid that constitutes their venom. Formica rufa is one such ant, but there are others with similar characteristics.
In the United States, the word pissant can refer to any small ant that infests a home.
In conversations with his advisors during the Vietnam War, U.S president Lyndon B. Johnson often referred to Vietnam as "that damn piss-ant little country." The word is used by lesser public figures as well: a Virginia politician once silenced a heckler by saying "I'm a big dog on a big hunt and I don't have time for a piss-ant on a melon stalk."