It seems that even when this "whisky frisky" phrase was being used in the 18th century, there was discussion over what it might mean.
In 1787, George Colman "the Elder" published a work titled Prose on Several Occasions; Accompanied With Some Pieces in Verse. In Volume II of this work is a parody called "Letter from Lexiphanes, containing Proposals for a Glossary or Vocabulary of the Vulgar Tongue, intended as a Supplement to a larger Dictionary."
This letter begins:
Tuesday, Dec. 4, 1770.
There are in every language, ancient and modern, certain heterogeneous words and anomolous expressions, which render it more difficult to be acquired by students and foreigners than even the most licentious idiomatick phrases, or the most irregular combination of sentences.
After further explanation, he continues:
To remedy this defect in English Literature, I have, with infinite labour, compiled a Vocabulary or Glossary, intended as a Supplement to a larger and more solemn Dictionary. It is easy to foresee that the idle and illiterate will complain that I have increased their labours by endeavoring to diminish them, and that I have explained what is more easy by what is more difficult -- Ignotum per, ignotius.
The letter writer presents a list of definitions for terms such as "higgled-piggledy" and "tit for tat" and "hodge-podge," after which he declares the need for such a dictionary by presenting examples of terms that yet need to be defined:
Philological Disquisitions are but ill adapted to the readers of a sugacious paper. Having, therefore already given a sufficient indication of my purpose to the Philosopher, the Academick, and the Scholar, I shall at present add no further interpretations; but in order to convince the learned of the Necessity and Importance of the work announced to them, I shall somewhat enlarge the catalogue of terms that demand explication; which like base metal among legitimate coin, have, by long usage, become current in our language; and without which the commerce of the world, or even the traffick of letters, can with difficulty be maintained either with profit or delectation. To explain them may be some glory: it would be more substantial fame to contribute to their extirpation.
He who writes the Dictionary of any Tongue, may be considered as labouring in a coal-mine; but he who collects the Refuse of a Language, claims more than ordinary commiseration, and may be said to sift the cinders.
I am, Sir,
The name "Lexiphanes" is a wordplay on the Greek words for "word" and "show" or "appear."
It might be worth noting that in the 18th century, the adjective "whisky" was not a nice way to describe someone.
The 18th century Lancashire satirist John Collier wrote under the pen name "Tim Bobbin." He is best known for A View of the Lancashire Dialect, or, Tummus and Mary (1746), which he followed up with The Lancashire dialect, or, The adventures and misfortunes of a Lancashire clown, which contains the indecipherable (if you're not a Lancastrian) exchange between Tummus (Thomas) and Meary (Mary):
T. Is't think on ot teaw looks o bit whisky, chez whot Seroh o'Rutchot's is.
M. I yeard um sey ot gexing's o knit' lying, un ot proof oth' pudding's ith' eyghting. -- So fareweel, Tummus.
A mid-19th-century revision by Samuel Bamford of the latter work, titled Dialect of South Lancashire: Or, Tim Bobbin's Tummus and Meary ; with His Rhymes and an Enlarged and Amended Glossary of Words and Phrases, includes a glossary that defines "whisky" as "frisky" or "immodest."
A similar revision by a different mid-19th-century author, John Corry, defines "whisky" as "whorish."