An irreversible binomial is a pair of words connected with a conjunction that would no longer have the same definition if the order was switched. Normally, something about the binomial makes it sound catchy: it can be alliterative, like with bed and breakfast (which would have a completely different meaning if it was breakfast and bed); synonymous, like with pins and needles; antonymous, like with mom and pop; rhyming, like with wine and dine; and with legal terms, such as cease and desist. All of these phrases need that particular ordering to work. Occasionally, irreversible binomials can be composed of proper nouns, like Adam and Eve, and irreversible trinomials are also a thing, including red, white, and blue, and life, liberty, and property. I think it's pretty cool how we form these unshakeable semantic associations in our heads.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.