"one devoted to precision," 1570s, from precise + -ian on model of Christian, etc., or from or based on French précisien. Especially "one who adhered punctiliously to rules or doctrines." Precisionist in the same sense is by 1827.
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.).
variant of suffix -an (q.v.), with connective -i-. From Latin -ianus, in which the -i- originally was from the stem of the word being attached but later came to be felt as connective. In Middle English frequently it was -ien, via French.
<a href="https://www.etymonline.com/word/precisian">Etymology of precisian by etymonline</a>
Harper, D. (n.d.). Etymology of precisian. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/precisian