13 letters · 19 points in Scrabble
noun the cheerful feeling you have when nothing is troubling you
noun the gracefulness of a person or animal that is quick and nimble
noun the trait of being lighthearted and frivolous
originFrom Middle English lightsomnesse, equivalent to lightsome (“light in weight, light-hearted, easy”) + -ness.
Etymology from Wiktionary, CC BY-SA 3.0