low profile vs on the sly

low profile

noun
  • An intentionally furtive position as to not arouse suspicion or catch attention. 

on the sly

adv
  • Slyly, in an inconspicuous manner, so as not to be seen; secretly; stealthily. 

How often have the words low profile and on the sly occurred in a corpus of books? (source: Google Ngram Viewer )