I was watching 'Pop-Up Videos' the other day, and one of the videos featured was Pat Benetar's "Love Is A Battlefield". There's one scene that shows Pat climbing some stairs, and it's so dark you can barely tell that it's her. The pop-up notes that a "gaffer" is a person who is responsible for lighting in a video production, leaving you to make the connection to the word "gaffe", which is a mistake. Time to take a look at these two seemingly related words:
gaffe:
A clumsy social error, a faux pas.
From the Old French, gaff, meaning hook.
Looking further into the word gaff, it also has a slang meaning of swindling someone by rigging a game. Probably by using a hook to alter a target.
gaffer:
Al electrician in charge of lighting on a movie or television set.
Probably an alteration of grandfather/godfather.
Absolutely no relation whatsoever. So it goes...