background vs on the line

background

adj
  • Less important or less noticeable in a scene or system. 

verb
  • To put in a position that is not prominent. 

  • To gather and provide background information (on). 

noun
  • One's social heritage, or previous life; what one did in the past. 

  • Information relevant to the current situation about past events; history. 

  • The image or color over which a computer's desktop items are shown (e.g. icons or application windows). 

  • A part of the picture that depicts scenery to the rear or behind the main subject; context. 

  • A less important feature of scenery (as opposed to foreground). 

  • A type of activity on a computer that is not normally visible to the user. 

on the line

prep
  • At risk, as in a contest or enterprise. 

  • Currently calling on the telephone. 

  • On one of the lines marked on a playing field or court; (by extension) within bounds. 

  • On a level with the eye of the observer, as of a picture hung in on a wall. 

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