Impertinent means rude in a way that oversteps your place. An impertinent question, impertinent of him, thoroughly impertinent.
It is old-fashioned and rather grand — it implies a hierarchy being breached, which is why it sounds most natural from somebody senior. An impertinent question is one that is none of the asker's business. Note that the literal meaning is not pertinent, and the sense of cheek came from asking about things that had nothing to do with you. Note impertinence.
1adjectiveimpertinentRude in a way that oversteps your place.
“The child was sent out of the room for giving impertinent answers to the headmaster.”
synonyms: impudent, presumptuous
impertinent is a quality of rudeness.
Latin impertinens is in- plus pertinens, from pertinere, to belong to. Something impertinent literally does not belong to the matter, and the sense of cheek followed.
Proto-Indo-European
*ten-
Latin
impertinēns
Old French
impertinent
Middle French
impertinent
Middle English
impertinent
English, today
impertinent
Middle English impertinent, from Middle French impertinent, from Old French impertinent, from Latin impertinēns; by surface analysis, im- + pertinent.
Etymology from Wiktionary, CC BY-SA