punctilio
A fine point in exactness of conduct, ceremony, etiquette or procedure.
countable, uncountable
[…]–but, a-propos, ſaid he—Shakeſpear is full of great things—He forgot a ſmall punctillio of announcing your name—it puts you under a neceſſity of doing it yourſelf.
Strictness in observance of formalities.
countable, uncountable
Alas! she little conceived that, though without any apparent levity or disregard to the world's censure, yet from an obsequiousness and acquiescence to the will and pleasure of others, into what thoughtless indiscretion and want of due punctilio she might be led; rendering her, in the case of Philimore and Oriana, by favouring them in their secret union, a most dangerous intimate!
Where it comes from
From Italian puntiglio, or Spanish puntillo, diminutive from Latin pūnctum (“point”).
Adapted from the Wiktionary entry punctilio (CC BY-SA 4.0).