The ampersand is also often used when addressing an envelope to a couple: "Mr. & Mrs. Johnson" or "Mary& Peter". According to Wikipedia, it is used by the The Writers Guild of America to denote when two writers collaborated on a specific script rather than just rewriting another author's work. In screenplays, two authors joined with &, collaborated on the script, while two authors joined with and, worked on the script at different times and may not have had any contact with each other at all.Michael Quinion, in 'World Wide Words' has this to say about it:
"This name for the character is surprisingly recent, not being known before the nineteenth century, though the character itself was in use long before printing was invented. It started life as a Roman scribe's abbreviation of the Latin "et", meaning "and", and became common in the early medieval period. It was later taken over as an abbreviation for the English word "and".
"Ampersand" is a contraction of "and per se, and". This sounds odd, but it's a continuation of a medieval convention in which Latin "per se", by or in itself, was often added to those letters that
could stand alone as words: A, I and O (as in "O for the wings of a dove"). "A per se, a", meant "a by itself makes the word a". Since it stood first in the recital of the alphabet, in the fifteenth and sixteenth centuries it came to mean a pre-eminent person or thing: It was common enough that it was contracted to "apersey", meaning the first, unique, or most distinguished person or thing."
It was usual in the eighteenth century to have children end their recital of the letters of the alphabet with "&", because it was so common. "
*Thanks to Michael Quinion of WORLD WIDE WORDS
World Wide Words is copyright (c) Michael Quinion 2009. All rights reserved. The Words Web site is at http://www.worldwidewords.org