“Let's burn that bridge when we come to it” – is this sort of idiom mixing considered a pun, and if so, does it have a specific name?
I couldn't come up with a short title, but the upside is that there is not much needed to be said in the body of the question! For @dmr (and others), it mixes “let's cross that bridge when we come ...
I saw a lot of usage of machinery, mechanism, to be used with similar meaning as techniques, ways, methods,.... For example, my math teacher said the machinery in the proof of some theorem is not ...
Assume we have a literary masterpiece that is abundant in symbolism and metaphors. Within this masterpiece, the author uses a brook running through a glade of trees to represent a couple of things ...