Green’s Dictionary of Slang

1. a flea.

1891		G.R. Sims ‘Tottie’ Dagonet Ditties 127: Then a bow-wow by her side, / Who till then had stood and tried / A ‘Jenny Lee’ to banish, / Which was on his ‘Jonah’s whale,’ / Gave a hydrophobic bark.
1923		J. Manchon Le Slang.
1932		‘P.P.’ Rhy. Sl. 7: Fleas – Jenny Lees.
1960		J. Franklyn Dict. of Rhy. Sl.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.

2. a key.

1932		‘P.P.’ Rhy. Sl. 5: Put yer Chalk Farm under the Rory O’Moore and find the Jenny Lee.
1960		J. Franklyn Dict. of Rhy. Sl.
1969		S.T. Kendall Up the Frog 20: ’E gets aht a Jennie Lee an’ in we goes into this ’ere birch broom.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.

3. tea.

1932		‘P.P.’ Rhy. Sl. 13: Tea – Jenny Lea.
1950		West. Australian (Perth) 11 Mar. 22/6: A man asks his mate to th Jenny Lee, the tea.
1960		J. Franklyn Dict. of Rhy. Sl.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.