Stephen Colbert, in his 7/25/18 monologue, uttered this one when discussing the Cohen tape on the Trump payoff of the McDougall matter. Here’s the link to the video:
It is a mashup of “in the heat of the moment” (doing something without thinking) and “the meat of the matter” (the most important or essential element of an issue or problem). “Heart of the matter” (same definition as “meat of the matter”) might also be in play, as “heart” and “heat” are similar in sound and looks. A big thanks to Sam Edelmann for hearing this one and sending it in.
This was heard on the Rachel Maddow show. Vanity Fair reporter Emily Jane Fox was talking about Michael Cohen, and what he may have on Trump. She then uttered this beauty. It is a congruent conflation of “close to the chest” and “under wraps” (to keep one’s plans secret from others). The vest/chest rhyme and close/under words probably contributed to the mix up. A big thanks to “Eagle-Ear” Frank King for hearing yet another one on MSNBC, your malaphor channel.