Meaning

adjective characterized by excessive precision and attention to trivial details

originFrom Scots pernickety, persnickety, apparently from per- + nick (“a notch, mark, cutting retort”) + -et (“-ed”) + -y; equivalent to English per- + nick + -ety; literally, “marked up”, then “overly precise”. The alternative form persnickety, with s, may be due to substitution of Scots sneck (“a cut, notch”) for nick. Compare also Scots variants pernicked, pernicket, pirnicky, and pernicky.

Etymology from Wiktionary, CC BY-SA 3.0