An ampersand is a logogram “&” representing the conjunction word “and”. This symbol is a ligature of the letters et, Latin for “and”.
The word ampersand is a corruption of the phrase “and (&) per se and”, meaning “and (the symbol &) intrinsically (is the word) and”.
Traditionally, in English-speaking schools when reciting the alphabet, any letter that could also be used as a word in itself (“A”, “I”, and, at one point, “O”) was preceded by the Latin expression per se (“by itself”). Also, it was common practice to add at the end of the alphabet the “&” sign as if it were the 27th letter, pronounced and. As a result, the recitation of the alphabet would end in “X, Y, Z, and per se and”. This last phrase was routinely slurred to “ampersand” and the term had entered common English usage by 1837.