Futile, a.
Etymology: [L. futilis that easily pours out, that easily lets loose, vain, worthless, from the root of fundere to pour out: cf. F. futile. See Fuse, v. t.]
1. Talkative; loquacious; tattling. [Obs.] Talkers and futile persons. Bacon.
2. Of no importance; answering no useful end; useless; vain; worthless. "Futile theories." I. Taylor. His reasoning . . . was singularly futile. Macaulay.
Shades of meaning
Fernald has no entry of its own for futile; he lists it under vain.
Where he writes about it:
That which is useless, futile, or vain is inherently incapable of accomplishing a specified result. — from vain