dropbox vs post box

dropbox

noun
  • A box wherein objects can be deposited by one person for later collection by another. 

  • A computer folder to which files may be dragged and dropped and from which users of other computers on the network can access those files. 

  • An enhancement to a loom that allows patterns of multiple colors to be woven from the same loom. 

post box

noun
  • A box or slot into which a courier or postal worker puts letters for a recipient to collect. 

  • A box in which post can be left by a sender to be picked up by a courier or postman (postal worker). 

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