This is a historical word. For it does touch upon a human existence from the time of Adam and Eve. But the word Cover must be associated with other pretext to complete the meaning of the word like saying cover up or other pretexts, which fall within the realm of spying.

Once the word Cover began to be attached to the word spy then it became very lucrative financially. For example here the name 007 became everybody's talk about combating spies around the world. This word became a household talk.

DR.HASHIM S.H. BEHBEHANI