The case
This one comes with a receipt. Generations of kids sang the spelling out loud, letter by letter, in the bologna jingle. M-A-Y-E-R. And still a large share of the same people will write Meyer without hesitating.
The company is named after its founder, Oscar F. Mayer, a German immigrant butcher in Chicago. Meyer is simply the more common surname, so the ear hears the familiar one.
Why our brains do this
Frequency wins. "Meyer" outnumbers "Mayer" as a surname, and spelling from sound defaults to the frequent form even when you once sang the letters.
Sources: Wikipedia — Oscar Mayer · Wikipedia — False memory: the Mandela effect
