This made me do my own investigating. The `csh` manual in 2BSD said "catenate" earlier in '79. Even before that, a comment in the ex (vi) 1.1 source code in 1

This made me do my own investigating. The `csh` manual in 2BSD said "catenate" earlier in '79. Even before that, a comment in the ex (vi) 1.1 source code in 1BSD (1978) says "catenate". So it looks like Bill Joy made the mistake! (and the Bell Labs people thought it funny?)