The name "SHEEP" is pun on the Lisp Algebraic Manipulator or LAM on which SHEEP is based. The package was written by Inge Frick, using earlier work by Ian Cohen and Ray d'Inverno. Jan E. Åman wrote an important package in SHEEP to carry out the Cartan-Karlhede algorithm. Unfortunately, this software works only on certain rather old computers and old and proprietary operating systems.
A more recent version of SHEEP, written by Jim Skea, runs under Cambridge Lisp, which is also used for REDUCE.