Green’s Dictionary of Slang

St. John’s Wood, London NW, a suburb often chosen by men to house their mistresses .

1891		Sporting Times 7 Feb. 3/3: The life’s so dull, so slow, so beastly good, / I must return to Brompton, or the ‘Wood’.
1905		Illus. Police News 30 Dec. 6/4: When a chap ain’t as a slow as a funeral hearse, / And runs a dear friend in ‘the Wood’.