Joel 2:2

The morning spread upon the mountains. — The Hebrew word here used for morning is derived from a verb, Shachar, which has for one meaning “to be or become black,” for the second “to break forth” as light. From this latter signification is derived the word for morning — dawn; from the former comes the word “blackness,” which gives the name Sihor to the Nile (Isaiah 23:3). It seems accordingly more in harmony with the present context to take the sense of the word in its reference to blackness, and to understand it as indicating a thick, dark, rolling cloud settled upon the mountain top. The description following comprehends equally the natural and political locusts.