A hidden agenda countable noun
Used to refer to a motive or goal that is secret or ulterior
I didn't trust Ken when he was suddenly nice to me, and I doubted he had a hidden agenda.
I feel there's a hidden agenda behind this plan.
Used to tell someone to keep secret what you're about to say
Try to hide and deny something that is embarrassing, unappealing, or damaging to one's reputation
To deliberately hide one's true nature, intentions or purposes
To be secretly working together
Many sources point to the late 1985s to the early 1900s for the origin of this phrase.