The following I posted in another thread, before realising that a search at the 'Cat did not turn it up.
Sources on the Net suggest an origin as a nursery rhyme at least back to the 17th century:
He is even memorialized musically: a folk song bearing his name was edited by Benjamin Britten in 1938. A nursery rhyme that can be first traced back to the late seventeenth century begins "Oliver Cromwell lay buried and dead, hee-haw, buried and dead."
From: This Site
The words quoted below are taken from the BBC 'Time & Tune' Schools broadcast booklet for Spring 1955, with the addition of a last verse from memory.


OLIVER CROMWELL LAY BURIED AND DEAD
(Trad)

Oliver Cromwell lay buried and dead,
Hee-haw, buried and dead,
There grew an old apple tree over his head,
Hee-haw, over his head.

The apples were ripe and ready to fall,
Hee-haw, ready to fall,
There came an old woman to gather them all,
Hee-haw, gather them all.

Oliver rose and he gave her a drop,
Hee-haw, gave her a drop,
Which made the old woman go hippety hop,
Hee-haw, hippety hop.

The saddle and bridle, they lie on the shelf,
Hee-haw, lie on the shelf,
If you want any more your can sing it yourself,
Hee-haw, sing it yourself.


CHEERS
Nigel