Brian Gaff submitted this idea :
And while I'm at it, ok so the piece it grapples is a grapple pin, but where
did the word that sounds like end-effector come from?

Strange terminology.

From being on the end of the arm, and being the effector of the
gripping action. That seems to be the term used by robots in Detroit
and Nagoya and elsewhere, rather than specific to the Canadarm.

/dps

--
Who, me? And what lacuna?