They provided the following background on this word:

"Tantivy" is also a noun meaning "a rapid gallop" or "an impetuous rush." Although its precise origin isn't known, one theory has it that "tantivy" represents the sound of a galloping horse's hooves. The noun does double duty as a word meaning "the blare of a trumpet or horn." The second use probably evolved from confusion with "tantara," a word for the sound of a trumpet that came about as an imitation of that sound. Both "tantivy" and "tantara" were used during foxhunts; in the heat of the chase people may have jumbled the two.

"In a headlong rush..."  If Paul had been writing in English he might have used this word in his letter to the believers at Corinth:

1 Corinthians 9:24-27

Do you not know that those who run in a race all run, but only one receives the prize? Run in such a way that you may win.  Everyone who competes in the games exercises self-control in all things. They then do it to receive a perishable wreath, but we an imperishable.  Therefore I run in such a way, as not without aim; I box in such a way, as not beating the air; but I discipline my body and make it my slave, so that, after I have preached to others, I myself will not be disqualified.

Perhaps Paul would have exhorted them to run in tantivity... in a headlong rush.

We have only this one life to live (Heb 9:27) and this one race to run.  There is no second race for which we should save our energy or our talents.  Just as Messiah came to serve and gave every bit of Himself even to the point of death (Php 2:8) so we, too, should give all we have and serve the Lord our G-d with all our heart, and with all our soul, and with all our might (Deut 6:5).  May we not be found at the end of our race having held anything back that He might say to each of us "well done, good and faithful servant..." (Matt 25:21 KJV).

Now to the King eternal, immortal, invisible, the only God, be honor and glory forever and ever. Amen.  (1 Tim 1:17)