Webster's Revised Unabridged Dictionary · 1913

Alacrity

Alacrity ({not transcribed}) , noun

[Latin alacritas, from alacer lively, eager, prob. akin to Greek {not transcribed} to drive, Gothic aljan zeal.]

A cheerful readiness, willingness, or promptitude; joyous activity; briskness; sprightliness; as, the soldiers advanced with alacrity to meet the enemy.
I have not that alacrity of spirit, Nor cheer of mind that I was wont to have. — Shakespeare