levis

Levis, leve is a third declension adjective of two terminations, the exact opposite of gravis and declined identically: levi in the ablative, levia in the neuter plural, levium in the genitive plural. Physical lightness leads to slightness, then to triviality, then to being unreliable, so a levis homo is a lightweight in the English sense.

There is a genuine second word here. Levis with a short first vowel is "light"; levis with a long one, from the same spelling in an unmarked text, means "smooth, polished" and is unrelated. Only context and metre separate them. Manuscripts write leuis for both. English levity, alleviate, elevate and lever come from the "light" one; levigate comes from the other.