Green’s Dictionary of Slang

whisky; note attrib. use in cit. 1892.

1886		Sporting Times 9 Jan. 5/4: Thirsting for a little Jack the Dandy, I’m so Frisky, Bryan O’Lynn or Finger and Thumb.
1892		‘Doss Chiderdoss’ ‘The Rhyme of the Rusher’ in Sporting Times 29 Oct. n.p.: He had been on the I’m so tap, and now / He was slightly elephant’s trunk.
1894		Pall Mall Gaz. 4 July 3/2: Other examples of [...] the simple form of rhyming slang are ‘cat and mouse’ (house) [...] and ‘’m so frisky’ (whisky).
1916		Yorks Eve. Post 16 Oct. 5/4: The jargon of the ‘Tommy’ [...] is a never-ending source of wonder to canteen workers and barmaids [...] A nip of ‘I’m so frisky’ means a drop of whisky. Inviting a friend into a public house, the soldier will say, ‘Let’s call in this peever’.
1937		Lester in DSUE (1984).
1960		J. Franklyn Dict. of Rhy. Sl.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1992		R. Puxley Cockney Rabbit.