The word pismire has experienced a two hundred-fold decrease in usage since its peak in the early 1800s. A very large majority of people today don't even know that it's an archaic word for "ant". And of those who do know, even less are aware of the fact that it's kind of redundant! It's a portmanteau of two words: pyss, meaning "urine" (and, yes, the forebear of modern piss), and mire, ironically also meaning "ant". So an old word for "ant" comes from "piss ant", making the pyss part completely useless. The connection to urine was apparently because of the pee-like smell of anthills. Now, mire comes from Old Norse maurr or myrr, with the same meaning. Then, through Proto-Germanic miuzijo, we can reconstruct it to Proto-Indo-European morwi, yes, still with the same definition. Now we just have to etymologize the word piss! It was a verb before it was a noun (and this transition is a fine instance of anthimeria). This comes from Old French pissier, from Latin pissiare, which also still meant the same thing. Allegedly, this is of imitative origin, meaning that the verb pissiare is supposed to sound like the action of micturition.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd