Knobs and Cables

I read the other day that an ampersand started it's life as a typographical ligature of the letters 'e' and 't' which in Latin spell 'et' meaning 'and'.
The word ampersand is apparently a corruption of the phrase 'and (&) per se and', meaning '(the character) & by itself (is the word) and.'
I had always wondered where it came from.
Also you should never use one unless you need one to keep your line length correct in typesetting, it is not supposed to be used to replace the word 'and' anywhere you want to. But opinion on that is divided.
Anyway that's why these are 'Knobs and Cables' as opposed to 'Knobs & Cables' which is what I was originally going to type until I remebered that you shouldn't use it willy nilly, unless you're Eric Gill of course.

Canon a520