means Excessive pride in one's appearance or achievements; also, the quality of being empty or worthless, as in vain effort or vain hopes.

from From Latin vanitas, 'emptiness, falseness, foolish pride,' built on vanus, 'empty, void' — the same root that gives us 'vain' and 'evanesce.' It reached English through Old French vanite. The double meaning is baked into the word: to be vain about your looks and to labor in vain both trace back to the same Latin emptiness. The famous biblical lament 'vanity of vanities, all is vanity' uses vanitas precisely in its older sense — not self-love, but futility, a chasing after wind.