I've always been fond of the old spelling "uisquebaugh" or its
variations. I don't know about the Regency. I know Gov. Alexander
Spotswood had a huge selection of it on his trip to explore the western
mountains of Virginia in the mid 18th. Random House dictionary dates it
"[1705 15; short for whiskybae < Ir uisce beatha or ScotGael uisge
beatha, ult. trans. of ML aqua vitae lit., water of life; cf. USQUEBAUGH]"

and it also says that whisky (neat, no e) is used especially for Scotch
and Canadian, but doesn't say preferred or anything like that