Layil (לֵיל, Strong's #3915), “night.” Cognates of this noun appear in Ugaritic, Moabite, Akkadian, Aramaic, Syrian, Arabic, and Ethiopic. The word appears about 227 times in biblical Hebrew and in all periods.
Layil means “night,” the period of time during which it is dark: “And God called the light Day, and the darkness he called Night” (Gen. 1:5—the first biblical appearance). In Exod. 13:21 and similar passages the word means “by night,” or “during the night”: “And the Lord went before them by day in a pillar of cloud … and by night in a pillar of fire, to give them light; to go by day and night.” This word is used figuratively of protection: “Take counsel, execute judgment; make thy shadow as the night in the midst of the noonday; hide the outcasts; [betray] not him that wandereth” (Isa. 16:3). Layil also figures deep calamity without the comforting presence and guidance of God, and/or other kinds of distress: “Where is God my maker, who giveth songs in the night …?” (Job 35:10).
During Old Testament times the “night” was divided into three watches: (1) from sunset to 10 P.M., (Lam. 2:19), (2) from 10 P.M. to 2 A.M. (Judg. 7:19), and (3) from 2 A.M. to sunrise (Exod. 14:24).