From Latin ultimus ('farthest, last'), itself the superlative of ulter ('beyond'), 'ultimate' entered English meaning 'final' and later acquired the sense of 'the greatest possible'.
Being or happening at the end of a process; final. Also: the best achievable or most extreme of its kind.
From Latin ultimatus, past participle of ultimare ('to come to an end'), from ultimus ('last, farthest'). Ultimus is the superlative form of the root ulter ('beyond, on the far side'), which also produced ultra. The Proto-Indo-European root is *al- ('beyond'), the same source as English else and Latin alter ('other'). English borrowed the word in the mid-seventeenth century with the sense 'final' or 'last in a series'. The intensified meaning of 'greatest, most extreme' developed in the eighteenth century, and the casual use for 'best possible' is a twentieth-century extension. Key roots: ultimus (Latin: "last, farthest").