|1253280. Thu Oct 05, 2017 4:37 pm
|A pernickety (British English), or persnickety (American English), person is someone who is 'exacting about details; particular, careful; punctilious; spec. putting excessive emphasis on trivial or minor details; fussy' in the OED. Naming no elves.
Pernickety is an older word, with its origins in Scots from the early 19th century with variations such as ‘pirnicky, pernicky, pernicked, pernicket, pernickett, pirnickerie, pernigglety, pick-nickerties, and pernicketies’ . From google ngrams viewer , pernickety’s usage in British publications surged in the early 20th century, peaking in the 1950s and has now roughly halved by 2008.
The American form, persnickety, came from the late 19th century and its usage has continued to grow since then, but not without controversy. In the 1934 edition of the Webster's New International Dictionary, the entry for pernickety was on page 1825  and persnickety should have been on page 1827 alphabetically. However, in those times, uncommon variations would be hidden away in the footnotes of the page. Persnickety, an uncommon variation of pernickety at the time, was banished to the footnotes of page 1825. When readers saw persnickety used in newspaper articles and could not find it in the dictionary, they wrote letters to the editors to complain. Complaints stopped when newer editions of the dictionary was published and persnickety was more visible.
Again, according to google ngram viewer , pernickety was the dominant form in US publications until the mid 1940s and has been declining since then. Persnickety might have had a bumpy start but its usage is currently as high as pernickety was in the 1940s, in US publications.
Regardless of usage and popularity, I just find both words funny to say out loud.
 Sayers, William. "Pernickety." Scottish Language 29 (2010): 87-91. https://www.questia.com/library/journal/1G1-283945517/pernickety
 Google ngrams viewer
 Gilman, E. Ward. "Dictionaries as a source of usage controversy." Dictionaries: Journal of the Dictionary Society of North America 12, no. 1 (1990): 75-84. https://muse.jhu.edu/article/456458/summary