The Free On-line Dictionary of Computing (30 December 2018):

first-in first-out
FIFO

    (FIFO, or "queue") A data structure or hardware
   buffer from which items are taken out in the same order they
   were put in.  Also known as a "shelf" from the analogy with
   pushing items onto one end of a shelf so that they fall off
   the other.  A FIFO is useful for buffering a stream of data
   between a sender and receiver which are not synchronised -
   i.e. not sending and receiving at exactly the same rate.
   Obviously if the rates differ by too much in one direction for
   too long then the FIFO will become either full (blocking the
   sender) or empty (blocking the receiver).  A Unix pipe
   is a common example of a FIFO.

   A FIFO might be (but isn't ever?) called a LILO - last-in
   last-out.  The opposite of a FIFO is a LIFO (last-in
   first-out) or "stack".

   (1999-12-06)