Have you ever said something was the only choice? Maybe you haven't said it yourself, but you've heard other people say it.
Have you ever thought about the phrase itself?
The "only choice"?
This is an oxymoron, where contradictory or very different words are used together. "Choice" is about having more than one option. "Only" refers to one sole thing. See how they are very different, even oppositional? If you're going to have choices, there is going to be more than one, so there's never only one choice really.
The "only choice" is an oxymoron, yet we understand how this figure of speech references something that makes sense; something that we can understand.
There can be a situation where, obviously, there are many things that one can do, but some of these things will not produce the result we want, or may even harm us or others. In such a case there is often only one choice to make out of the many because it is the best choice to make.
There may not "only" be one choice to make, but sometimes there is clearly a better and optimal choice to make, which makes it the "only choice" a rational and reasonable person would choose compared to the alternatives.
Sometimes language is really weird like that. We can put two things together that normally wouldn't make sense together, but because of a certain context or situation, two oppositional words can unite to provide greater definition about that situation being referenced.
I enjoy learning about how language functions to provide meaning and definition to aspects of reality that we want to communicate about. Word symbols summon imagery into our "minds" and invoke emotions into our "hearts" (consciousness). Words influence us like a spell (spelling), to affect our thinking, feeling and behavior. Language is powerful!