Green’s Dictionary of Slang

turning-tree n.

the gallows.

1542		Hall Henry VIII f. 224 n.p.: And at the last, she and her husband [...] were [...] hanged at the foresayd turnyng-tree [F&H].
1569		R. Grafton A chronicle at large 1224: [S]he and her husbande as they deserued, were apprehended, arraigned and hanged at the foresayde turning tree, where she hanged stil & was not cut downe.
1580		J. Stow Chronicles 1002: [see prev.] Woolfe and his wife were hanged on two Gibbets, at the turning trée in Lambeth Marshe, for murthering the two Merchant strangers aforesaide.