The master, (Po I think) used this as a term of endearment and comparison when speaking to his student the youns Kwai chen cain who (played by David Carradine (post Shane) was a novice monk (Shaulin or some word) and in subsequent movies this has been referenced.
It isn't a term used in 'typical Kung Fu flicks', it was used in the American TV series titled 'Kung Fu', as above. If you've seen it in other films, they're probably spoofs of that series.
Thanks to dot.hawkes & alfiebrady, that really explains a lot. And I retract that last comment of the term being in a typical kung fu film. It's just the word that would be forever referred to in Kung Fu.
I remember a scene where thingie (David Carridine) and the master were in the temple. The master is blind and he's waffling on about the usual monk sort of gubbins and then he says 'can you hear the grasshopper at your feet'. His pupil looks down and there is a grasshopper there (because the Master has got extra-sensory shaolin perception). Also he can fire lightening bolts out of his fingers.