The expression “silly goose” refers to a person who acts in a childish, foolish but somewhat comical way. This term originates from several sources. The entry in the Brewer's Dictionary of Phrase and Fable states, “A foolish or ignorant person is called a goose because of the alleged stupidity of this bird." The Samuel Johnson dictionary describes geese as, “Large waterfowl proverbially noted, I know not why, for foolishness."
Though the nursery rhyme character Humpty Dumpty is commonly portrayed as an egg, he is never explicitly described as such in the short rhyme; some theories hold that the inspiration for the rhyme can be traced back to a military cannon or to King Richard III, who is known to have had a hunched back, or humpback. The story of the cannon holds that an English man singlehandedly defended his town from an advancing army with the help of a cannon perched on top of a wall. However, the heavy cannon eventually fell down off the wall and couldn't be lifted back up, after which the townspeople had to surrender.
Rather than having a specific meaning, the "Hickory, Dickory, Dock" nursery rhyme seems to simply be a nonsense poem focused on rhyming more than narrative. The "dock" part of the rhyme clearly rhymes with "clock," while "hickory" and "dickory" rhyme, forming a simple rhyme scheme.