2SWAP
* 2SWAP ( a,a b,b -- b,b a,a )

double-cell swap, see SWAP and 2DUP
 simulate:
   : 2SWAP LOCALS| B1 B2 A1 A2 | B2 B1 A2 A1 ;

FORTH/ANS core (dpANS.6.1.0430) ordinary primitive