'punctiliousness' originates from English, specifically formed from the adjective 'punctilious' plus the noun-forming suffix '-ness'. 'Punctilious' ultimately derives from Italian 'punctilio' (also found as 'puntiglio'), which traces back to Late Latin 'punctum' meaning 'point'.

'punctiliousness' developed from the English adjective 'punctilious' (late 18th century). 'Punctilious' was formed from the noun 'punctilio' borrowed from Italian (or Spanish/Italian 'puntiglio'), itself coming from Latin 'punctum' ('point'); the suffix '-ness' later produced the abstract noun 'punctiliousness'.

Initially the root sense related to a 'small point' or 'minute detail' (from Latin 'punctum' and Italian 'punctilio'); in English this evolved into 'punctilious' meaning attentive to such small points, and into 'punctiliousness' meaning the quality of that careful attention.