From an unused root (meaning to be empty); a vacuity, i.e. (superficially) an undistinguishable ruin -- emptiness, void.
H922. bohu
בֹּ֫הוּ noun [masculine] emptiness (on form see Ges§ 84a, 1 b Sta§ 95, 198 a, on usage compare LagOr. ii. 60 f.) always with תֹּהוּ q. v.; — וָבֹהוּ תֹּהוּ Genesis 1:2 of primeval earth; Jeremiah 4:23 of earth under judgment of ׳י; בֹהוּ וְאַבְנֵי קַותֿֿהֹוּ Isaiah 34:11, the line of wasteness and the stones of emptiness, i.e. plummets, employed, not as usual for building, but for destroying walls; compare Di & see below אבן 6