on the QT vs secretly

on the QT and secretly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
on the QT	No	No	No	Yes
secretly	No	No	No	Yes

As adverbs, on the QT and secretly are synonyms defined as:

Other synonyms of on the QT include in secret, on the Q.T..

on the QT (adverb)	secretly (adverb)
in secrecy; not openly	in secrecy; not openly
	not openly; inwardly