Malaphor

A malaphor is a blend of two idioms into a third: "we'll burn that bridge when we come to it", "it's not rocket surgery", "that's the way the cookie bounces". The term was coined by Lawrence Harrison in a 1976 newspaper piece. The blend is funny because both parents stay recoverable and the result is nearly coherent.

It has three relatives, and separating them is a small Taxonomy worth having. An eggcorn, named by Geoffrey Pullum in 2003 after one person's spelling of acorn, is a substitution that makes its own sense: for all intensive purposes, old-timers' disease. A snowclone is a reusable template rather than a fixed phrase — "X is the new Y" — a cliché with a slot. A mixed metaphor blends images rather than set phrases. Only the eggcorn requires the speaker to have built a working reinterpretation; the others need no analysis at all.

Blends are independently reinvented, which is the interesting part. Idioms appear to be stored whole but retrieved by meaning, so two phrases with one meaning are live candidates at the same instant and can be spliced mid-production. Because the meaning survives the splice, listeners understand it, laugh and repeat it — so a blend spreads by transmission as well as by reinvention, and its frequency says nothing about a single origin. That is the trap in Folk Etymology too, where a satisfying story outruns its Provenance.

The pattern marks the limit of fluency without a plan: a locally well-formed string can be assembled from parts that do not belong together, which is what a Markov Chain does on purpose.