Reply to post: it was a button with 'I' and 'O' on it

it was a button with 'I' and 'O' on it

That's not an 'I' and 'O', that's a 1 and a 0. Presumably thought up by some techie who can only think in binary, and assumes everybody else will understand it too. There can't be any other reason, unless they thought that users wouldn't be confused as to whether 'O' stands for On or Off.