I always thought it was the way louise jones spelt it, cos this question bugged me for ages and when I finally found out the answer I always remembered it as a 'pencil'
It's actually 'Statler' as they are both named after hotels, the Statler and Waldorf-Astoria in New York. Astoria was also the name of Waldorf's wife and Statler's sister (i.e they are brothers-in-law)
LouiseJones is correct, it's Staedtler, because I'm deaf and never heard it pronounced out loud, but always thought of it as being prnounced "Stayed-ler", whereas if it was spelt the other way I'd think of it as "Statt-ler".