That’s a reference from the original TV movie, “Kung Fu”, which was effectively the pilot for the series. The blind Master Po tells young Kwai Chang to close his eyes then asks him if he can hear his own heartbeat. Kwai Chang says that he can. Masterp Po then asks him if he can hear the grasshopper besides him. Kwai Chang can not, then looks and sees the grasshopper that Master Po could hear. Thereafter Master Po called Kwai Chang “Grasshopper.”
That’s a reference from the original TV movie, “Kung Fu”, which was effectively the pilot for the series. The blind Master Po tells young Kwai Chang to close his eyes then asks him if he can hear his own heartbeat. Kwai Chang says that he can. Masterp Po then asks him if he can hear the grasshopper besides him. Kwai Chang can not, then looks and sees the grasshopper that Master Po could hear. Thereafter Master Po called Kwai Chang “Grasshopper.”