Pertness, n.
Rowlandson called this man "a lump of impertinence." What is he saying with his face?
A Lump of Impertinence!, Thomas Rowlandson, September 30, 1809. The Met.The quality or state of being pert.
Shades of meaning
Liveliness and sprightliness are pleasant and commendable; smartness is a limited and showy acuteness or shrewdness, usually with unfavorable suggestion; pertness and sauciness are these qualities overdone, and regardless of the respect due to superiors. Impertinence and impudence may be gross and stupid; pertness and sauciness are always vivid and keen. Compare impudence.