Stephenson:Neal:Quicksilver:660:Elixir Vitae and usquebaugh (jere7my tho?rpe)

From the Quicksilver Metaweb.

Elixir Vitae is the ultimate goal of alchemists and the imputed contents of the Philosopher's Stone, capable of granting eternal life and transmuting base metals into gold. Literally translated, it means "elixir [potion] of life".

Usquebaugh is whisky (from Gaelic, "uisge beatha"). Literally translated, it means "water of life".

Roger was making a cross-language pun: i.e., Daniel accused Isaac of drinking the elixir of life, so Roger pointed out that Daniel had himself been drinking the water of life.