Odd is, in many ways, an odd word. It’s the opposite of even, referring to a number not divisible by two. But it can also mean strange. As well as those two common meanings, in some dialects of English it can mean occasional or infrequent. Consider the Australian Vietnam-War movie The Odd Angry Shot. In Ireland, we might say something like I only go to the cinema the odd time now, because it’s so expensive. These disparate meanings are all interconnected though.
The original meaning of odd was third or additional number, coming from the old Norse oddi. This of course is also where we get the term odd number from. The first use of odd to mean strange seems to have occurred in the late 16th century, coming from the term odd man out, itself a reference to a third man in addition to a pair. Which of course is where the term third wheel (or occasionally fifth wheel, which in this automotive era probably now makes more sense), meaning someone awkwardly in the company of a couple, or couple-to-be.
It’s not hard to imagine odd coming to mean strange in general from that. We really like symmetry. We have a general tendency to find symmetrical faces more attractive, though that’s not always true. But I think we can all recognise that there’s something inherently satisfying about a matching pair. Think about how annoying it is to find an odd sock in your laundry. And that extends to order in general. Our brains seem to crave it, at least visually. Picture a pattern of tiles using two colours, with one tile out of place. A supposedly oval or circular pattern which is slightly off centre. Two angles that don’t quite meet. Your loose change thrown on the table, with one coin landing farther away than the others. Can you really resist leaving it there, and not putting it back with its friends?
The number three seems to be a bit of an exception, partly I think because of its religious uses, but also because it’s the lowest number of things you can use to easily make a circle. And we like circles, as long as they’re real, symmetrical ones.
It’s an interesting sign of how language is shaped by our psychology. We don’t like odd numbers, and therefore the word odd comes to mean strange. I wouldn’t be surprised if other languages do something similar. Perhaps you can enlighten me about such an oddity in your language, if it exists.