Left bow radical - pictograph of an archer's bow with string drawn back. The indexing radical and the literal semantic anchor: 弧 originally named a wooden bow before generalising to any curved shape. Sits alongside 弯 (bend), 张 (draw a bow), 弹 (shoot).
Right 瓜 supplies the sound guā -> hú through a regular k-/h- alternation. Pure phonetic; the melon meaning has no bearing on arcs and curves. Same phonetic family appears in 孤 (alone) and 狐 (fox) - all sharing the right-side gourd.
