A pissant, also seen as piss-ant has its origin the word pismire, a 14th-century term for ant. The term is also used as an insulting noun, and a pejorative adjective.
The original pissant is any of a certain group of large ant species, commonly called wood ants, that make mounded nests in forests throughout most of Europe. The name pissant arises from the urine-like odor produced by their nesting material—needles and straw from pine trees—and the formic acid that constitutes their venom. Formica rufa is one such ant, but there are others with similar characteristics. It may be derived from the term pismire. Forelius and Iridomyrmex are two genera of piss ants. In the United States, the word pissant can refer to any small ant that infests a home.
A derived meaning of the word is something that is insignificant, though the term is sometimes considered vulgar.