Indefatigable vs. Infatigable — What's the Difference?

Having or showing a capacity for persistent effort; not tiring or relenting

(obsolete) indefatigable

Extremely persistent and untiring.

Indefatigable.

Incapable of being fatigued; not readily exhausted; unremitting in labor or effort; untiring; unwearying; not yielding to fatigue; as, indefatigable exertions, perseverance, application.

Showing sustained enthusiastic action with unflagging vitality;