Hickory, dickory, dock,
The mouse ran up the clock.
The clock struck one,
The mouse ran down!
Hickory, dickory, dock.
Nursery rhyme origin
Like many poems and rhymes this one tries to imitate a particular sound, in this case the ticking of a clock.
It was a favourite poem of Sir Walter Scott who used to recite it to Marjorie Fleming, the diarist.