punctilio
Concise Oxford English Dictionary © 2008 Oxford University Press:
punctilio /pʌŋ(k)ˈtɪlɪəʊ/
▶noun (pl. punctilios) a fine or petty point of conduct or procedure.
– origin C16: from Ital. puntiglio(n-) and Sp. puntillo, dimin. of punto ‘a point’.
'punctilio' also found in these Oxford entries:

