This nursery rhyme dates back to 1810 and became famous in Lewis Carroll's 'Alice through the looking glass'. The legend of Humpty, however, goes back much further.

One thought is that it was a big cannon in the English Civil War that played a crucial role in the siege of Colchester in 1648.
That summer, the royalists led by the Earl of Norwich retreated to Colchester after being attacked by the parliamentarians commanded
by Lord-General Thomas Fairfax.
Colchester was rapidly blockaded by Fairfax and on June 13 he launched a ferocious attack. His forces were, however, devastated by
a withering bombardment from a big cannon, Humpty Dumpty, placed in the tower of St. Mary's church, which guarded a key approach to the town. Fairfax was forced to retreat. But on July 15
his artillery blasted an enormous hole in the church. Humpty crashed to the ground and smashed. And all the king's troops were unable to repair or remount it. So the royalist lost their most powerful weapon. The royalist position grew increasingly hopeless and on August 28 Fairfax took the town.