E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Silly is the German selig (blessed),
whence the infant Jesus is termed “the harmless silly babe,” and sheep are called “silly,” meaning harmless or innocent. As the “holy” are easily taken in by worldly ounning, the word came to signify “gullible,” “foolish,” (See SIMPLICITY.)
