Albert Barnes Commentary Psalms 55:5

"Fearfulness and trembling are come upon me, And horror hath overwhelmed me." — Psalms 55:5 (ASV)

Fearfulness and trembling - Fear so great as to produce trembling. Compare to the notes on Job 4:14. He did not know when these things would end. He did not know how far the spirit of rebellion had spread, and he had no means of ascertaining. It seemed as if he would be wholly overthrown, as if his power was wholly at an end, and as if even his life was in the greatest peril.

And horror has overwhelmed me - Margin, as in Hebrew, “covered me.” That is, it had come upon him so as to cover or envelop him entirely. The shades of horror and despair spread all around and above him, and all things were filled with gloom. The word rendered “horror” occurs only in three other places: Ezekiel 7:18, rendered (as here) “horror”; Job 21:6, rendered “trembling”; and Isaiah 21:4, rendered “fearfulness.” It refers to that state when we are deeply agitated with fear.