From Irish 'uisce beatha' (water of life), a calque of Latin 'aqua vitae' — the alchemists' name for distilled spirits. Shortened from 'uisce' to 'whiskey' through anglicization. The same 'water of life' metaphor gave French 'eau-de-vie', Scandinavian 'akvavit', and Russian 'vodka'.
A spirit distilled from fermented grain mash, typically aged in wooden casks.
From Irish 'uisce beatha' or Scottish Gaelic 'uisge beatha', meaning 'water of life'. This is a direct calque of Medieval Latin 'aqua vitae' (water of life), the alchemists' term for distilled spirits. The word was progressively shortened: 'uisce beatha' → 'uisce' → 'fuisce' → anglicized 'whiskey'. The spelling 'whiskey' (with an 'e') is standard in Ireland
The 'water of life' metaphor for spirits exists in at least six European languages independently: Irish 'uisce beatha' (→ whiskey), French 'eau de vie' (→ brandy), Scandinavian 'aquavit', Russian 'vodka' (from 'voda', water), and even Welsh 'dŵr bywyd'. Every culture that discovered distillation reached for the same metaphor.