A ‘ligature’ is the combination of more than one letter into a single symbol.
Roman scribes wrote the Latin word ‘et’ by combining the two letters into a ligature.
There are many theories about how this development evolved into the symbol we use today (and which part of the symbol is the ‘e’ and the ‘t’).
The earliest known variation was preserved by the eruption of Vesuvius in 79AD as graffiti on a wall in Pompeii.
For many years it was included as the 27th ‘letter’ of the alphabet and would apparently be recited by children as ‘and per se and’ (and in itself and).
The pronunciation of this was slurred by children and became known as the ‘ampersand’. Other apparent pronunciations included: And-pussy-and, Ann Passy Ann, anpasty, andpassy, ampassy, apperse-and, and zumzy-zan.
Today you might know it as the ‘and sign’.