Spirt

or spurt , “to put on a spirt ,” to make an increased exertion for a brief space, to attain one's end; a nervous effort. Abbreviation or shortening of spirit , or allusion to a spirt  of water, which dies away as suddenly as it rises.

“So here for a man to run well for a spurt , and then to give over ... is enough to annul all his former proceedings, and to make him in no better estate than if he had never set foot into the good waies of God.”—Gataker's Spirituall Watch, 4to. 1619, p. 10.