In the phrase which might be represented by the abbreviation "a w f a g's b", what does the "b" stand for?

Question

Which phrase that first came to public attention as a U.S. television commercial for the Wendy's chain of hamburger restaurants in 1984 became associated with the 1984 U.S. presidential election when Walter Mondale ridiculed Gary Hart's candidacy?

Answer 1

Bridle
The phrase is "a wigwam [or whimwham] for a goose's bridle", meaning "something nonsensical".