It is now called bourtree in Scotland, from the central pith in the younger branches which children bore out so as to make pop guns:- "Bour tree-Bour tree: crooked rung, Never straight, and never strong; Ever bush, and never tree Since our Lord was nailed on thee."
"Herbal Simples Approved for Modern Uses of Cure"
William Thomas Fernie
A little behind went Connoway, in the same manner holding a "bourtree" pop-gun which he had just been fashioning for some lucky callant of his acquaintance.
"The Dew of Their Youth"
S. R. Crockett
In Scotland this tree is known as the bourtree, and hence the rhyme- "bourtree, bourtree, crooked wrung, Never straight and never strong; Ever bush and never tree, Since our Lord was nailed to thee."
"The South Isles of Aran"
Oliver J. Burke