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.
The main thrust of the poem seems to be focused on introducing children to the concept of time in a memorable way rather than actually telling a story. The alliteration and simple rhyme scheme in the poem help make the words memorable, even for youngsters. First published in the 1700s, this poem likely originates from the United States.