Here we go round the prickly pear
Prickly pear prickly pear
Here we go round the prickly pear
At five o’clock in the morning.
                        – The hollow men

prickly pear, n.
Any of various spiny, sometimes tree-sized, cacti of the genus Opuntia (see Opuntia n.), having jointed stems that typically have flattened oval segments, and which are cultivated in warm countries for their fruit, as hedging, and (formerly) as host plants for the cochineal insect (also prickly pear cactus, prickly pear tree). Also: the pear-shaped fruit of any of these cacti, which is edible in some kinds.

-“prickly pear, n.” OED Online. Oxford University Press, December 2014.