carton vs letterbox

carton

noun
  • An inexpensive, disposable box-like container fashioned from either paper, paper with wax-covering (wax paper), or other lightweight material. 

  • A cardboard box that holds (usually 24) beer bottles or cans. 

  • A pack of cigarettes, usually ten, wrapped in cellophane or packed in a light cardboard box. 

verb
  • To put in a carton. 

letterbox

noun
  • A hidden container that holds a logbook and rubber stamp, found by following clues as a form of recreation. 

  • A rectangular hole or slot. 

  • A delivery point for mail, a box, compartment or slot for this purpose. 

  • A collection point for mail intended for onward delivery, a secure box or receptacle for this purpose. 

adj
  • Transferred to home video formats while preserving the original aspect ratio, having black bars above and below the picture area. 

verb
  • To transfer a widescreen motion picture to home video formats while preserving the original aspect ratio, with the placing of black bars above and below the picture area. 

  • To hunt for letterboxes (containers with logbook and rubber stamp) by following clues. 

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