levity

keveys

piristys Lightness of manner or speech, frivolity; lack of appropriate seriousness; inclination to make a joke of serious matters.
puhekieltä Lack of steadiness.
The state or quality of being light, buoyancy.
F. Scott Fitzgerald

Most of the confidences were unsought - frequently I had feigned sleep, preoccupation or a hostile levity (..)

(..)it would really seem as if there was something nomadic in our natures, a principle of levity and restlessness (..)

Hydrogen (..) rises in the air on account of its levity.