More importantly as not discussed, the '&' character also derives also from the french word 'et' which refers to 'and' in English. Something we can call a Norman influence.
The ampersand goes back farther than that. It comes from the Latin et (unsurprisingly also meaning and) and dates to the first century AD.
Hence why you sometimes see 'et al' rendered as '& al' (although it doesn't look right at all with the crappy ampersand in the font firefox is using here)