Also see definition of "Apace" in Word Study
Apace
APACE [isbe]
APACE - a-pas' ("at a pace"): With "come," 2 Sam 18:25; "flee," Jer 46:5, for "rapidly," "hastily," "fast," corresponding to a Hebrew idiom that adds emphasis or intensity to an idea by repetition of the word or its equivalent.
Also see definition of "Apace" in Word Study