H. T. Webster created a character called Caspar Milquetoast in 1924 for his cartoon series The Timid Soul - a play on milk and toast. The term milquetoast came to represent a timid or meek person in the US, playing off the bland nature of the dish - milk and toast. The usage of the word dipped around the middle of the century, though, with other words like wuss becoming more common.
Webster described Milquetoast as someone who “walked softly and was a beaten with a big stick”. This is, of course, a play on “big stick ideology” - Theodore Roosevelt’s foreign policy.