seriosity
/ˌsɪərɪˈɒsɪti/noun
The quality or state of being serious, now especially in a pompous or affected way; (excessive) seriousness.
Origin
Early 16th century; earliest use found in Robert Henryson (d. c1490), poet. From post-classical Latin seriositas from seriosus + classical Latin -tās. Compare Middle French or French †sériosité.