ἐλαφρόν  [1 verses] (adj sg neut nom​) "Light" is elaphros, which specifically means "light in weight," "easy to bear," "not burdensome," "easy," "light in moving," "nimble," "light minded," "thoughtless," "relieved" of a burden, and as an adverb, "lightly," "buoyantly."  - This is the only time Christ uses this word for "light." It means "light in weight," but when specifically applied to burdens, it means relieving them. It also means "simple-minded" when applied to thinking, which may be a larger topic here.