Word pairing
An unexpected pairing of two words never meant to sit together — the oxymoron's extended family.
Word pairing brings together two terms usage keeps apart, without their being necessarily contradictory: "a ferocious gentleness," "a monastic luxury," "a murderous politeness." The oxymoron is its extreme case (frontal contradiction); word pairing covers the whole spectrum of improbable neighborhoods.
It's one of stylistic invention's fundamental gestures: new meaning is born from the friction of old words. Great titles are often one — two words that didn't expect each other create a promise. The success criterion is simple: the pairing must open a meaning, not merely surprise.
Example
"A ferocious gentleness"; "a monastic luxury."