On the sly and Under wraps

On the sly adverb - In a furtive manner.

Under wraps and on the sly are semantically related. in secret topic. In some cases you can use "Under wraps" instead the phrase "On the sly" as an adjective or an adverb, when it comes to topics like sneaky, underground, clandestine.

Under wraps adjective - Kept secret.

On the sly and under wraps are semantically related. Sometimes you can use "On the sly" instead the phrase "Under wraps" as an adverb or an adjective.