Winnie the Pooh

Mr. Sanders is the name above the door at the house of Winnie the Pooh in the children's books by A.A. Milne. When Milne says that Pooh lived under the name of Sanders, he means it quite literally, and is not suggesting that Pooh's surname was Sanders or that he took on an alter ego. In classic Pooh-writing, the N and the final S are often both written backwards.

The sign was present when Pooh moved in to the house, and is the name of the previous occupant - possibly also a bear due to the excellent conditions for quality of bear life there.

The Real Mr.Sanders

It is suggested that the name was taken from a Frank Sanders who owned a printing works in Snow Hill, London. He was a friend of Milne's illustrator, E.H. Shepard, and he printed some of Milne's work - though not his four Pooh books, which were printed by Jarrold of Norwich.


Sources:
http://www.lavasurfer.com/pooh-faq2.html