levity

Etymology

Coined in 1564, from Latin levitās (“lightness, frivolity”), from levis (“lightness (in weight)”). Cognate to lever, and more distantly, light.

noun

1. Lightness of manner or speech, frivolity; lack of appropriate seriousness; inclination to make a joke of serious matters.
2. (obsolete) Lack of steadiness.
3. The state or quality of being light, buoyancy.
   […]it would really seem as if there was something nomadic in our natures, a principle of levity and restlessness […] 1838, Robert Montgomery Bird, Peter Pilgrim
   Hydrogen […] rises in the air on account of its levity. 1869, Mary Somerville, On Molecular and Microscopic Science, 1.1.12
4. (countable) A lighthearted or frivolous act.
   For though it be something wonderful to tell that any should have hearts so hardened, in the midst of such a calamity, as to rob and steal, yet certain it is that all sorts of villainies, and even levities and debaucheries, were then practiced in the town as openly as ever: I will not say quite as frequently, because the number of people were many ways lessened. 1665, Daniel Defoe, A Journal of the Plague Year, Gutenberg
   […] or do the people joy less than common in their levities?" 1872, J. Fenimore Cooper, The Bravo
   His incorrigible levities had probably lost him the countenance of most of his more serious acquaintances[…]. 1882, H.D. Traill, Sterne