FEARFULNESS.The adj. fearful is often used in AV [Note: Authorized Version.] in the sense, not of causing fear, but of feeling it: and fearfulness always denotes the emotion of fear. Thus Mat_8:26 Why are ye fearful, O ye of little faith?; Psa_55:5 Fearfulness and trembling are come upon me. In the RV [Note: Revised Version.] of the NT the only meaning of fearful is full of fear, the Revisers, Westcott tells us, having purposely retained this use in order that fear, fearful, and fearfulness might all agree in meaning. They have accordingly changed fearful sights in Luk_21:11 into terrors. The Revisers of the OT, however, had no such thought, and they have left the word unchanged.
Hastings' Dictionary of the Bible
Edited by James Hastings, D.D. Published in 1909