mid-15c., "neither more nor less than, with no error; exactly stated or marked off; definitely or strictly expressed; distinguished with precision from all others," from Old French précis "condensed, cut short" (14c.) and directly from Medieval Latin precisus, from Latin praecisus "abrupt, abridged, cut off," past participle of praecidere "to cut off, shorten," from prae "before" (see pre-) + -cidere, combining form of caedere "to cut" (from PIE root *kae-id- "to strike"). For the Latin vowel change, see acquisition. Related: Precisely (late 14c.).
word-forming element denoting action, quality, or state, attached to an adjective or past participle to form an abstract noun, from Old English -nes(s), from Proto-Germanic *in-assu- (cognates: Old Saxon -nissi, Middle Dutch -nisse, Dutch -nis, Old High German -nissa, German -nis, Gothic -inassus), from *-in-, originally belonging to the noun stem, + *-assu-, abstract noun suffix, probably from the same root as Latin -tudo (see -tude).
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Definitions of preciseness
clarity as a consequence of precision;
the quality of being reproducible in amount or performance;
he handled it with the preciseness of an automaton