Meaning

noun a punctuation mark (&) used to represent conjunction (and)

originA mondegreen of and per se and, ⟨&⟩ being read as “and”. Letters used by themselves were formerly mentioned according to this pattern, as in “O per se O” for the particle O or “I per se I” for the pronoun I. “And per se and” thus meant ⟨&⟩ by itself, as opposed to forms such as &c. The specific form ampersand is first attested in 1795, originally as a mocking pronunciation spelling, but this name…

Etymology from Wiktionary, CC BY-SA 3.0