couch (something) in (something)
To convey something very deliberately by saying it in a particular way or with particular wording. That professor always manages to couch her criticism in kind words, so I'm never too upset by her negative feedback.
couch something in something
to express something in carefully chosen or deceptive words. He tended to couch his explanations in arcane vocabulary. She couched her words in an overly polite manner.