flow
滮 centers on the idea of flowing, especially of water moving in a stream or current.
滮 is a phono-semantic compound: the water radical 氵 indicates the meaning 'flow', while 彪 likely contributes the sound. The exact historical development is uncertain.
Water 氵 flows beside a 彪, a tiger-like shape with stripes that suggest rippling currents. Imagine a tiger's stripes flowing like water.
For ヒョウ, picture a hyō (雹, hail) storm making water flow rapidly: hyō -> ヒョウ, and the hail melts into flowing streams.