Many years ago, when I became offended at the odd "abbreviated forms" people used as replacements for the &, I decided to look it up and found that that particular symbol was at that time traced back to pre-biblical Egyptian/Arabic glyphs.
As numerous things, such as the invention of the typewriter, the sewing machine, the helicopter, and recyclable paper - and the rise of the internet, have intervened since I learned to write one in script, it's quite likely that history also has changed and different origins may be found now.