The various terms used describe God as an object of the most implicit and reliable trust.
rock - literally, “a cleft rock,” for concealment.
strength - a firm, immovable rock.
horn of my salvation - The horn, as the means of attack or defense of some of the strongest animals, is a frequent emblem of power or strength efficiently exercised (compare Deu 33:17; Luk 1:69).
tower - literally, “high place,” beyond reach of danger.