To exchange two things, each for the other; to swap places. If you
point to two people sitting down and say Exch!
, you are
asking them to trade places. EXCH, meaning EXCHange, was originally the
name of a PDP-10 instruction that exchanged the contents of a register and
a memory location. Many newer hackers are probably thinking instead of the
PostScript exchange operator (which is usually
written in lowercase).