Term for mentioning X by saying "I will not say X" [duplicate]

Solution 1:

Apophasis is exactly what you seek. To borrow the definition from Chambers, it means "effectively saying something by stating that you will not mention it."

It is a commonly-used word in theology: a description of God is apophatic when He is described using what He is not.

EDIT (adding another answer after FumbleFingers' comment) - Paralipsis. Once again borrowing Chambers definition, "A rhetorical figure by which one fixes attention on a subject by pretending to neglect it, as in ‘I will not speak of his generosity’, etc." I concur with FF that this is a better fit than Apophasis for OP's question.