Left indexing foot radical - a pictograph of a leg with the foot at the bottom. Anchors 蹦 firmly in the locomotion family alongside 跑 (run), 跳 (jump), 踢 (kick), 走 (walk). When the radical is foot, the verb concerns motion of the feet.
Right 崩 supplies the sound (bēng → bèng with tone shift). 崩 itself means "mountain crumbling" - 山 over 朋 - and the cascading-rocks imagery lends a faint flavor: a jump is the body bursting upward like a stone-fall reversed. Almost identical phonetic.
