那（nà,that）个（gè,one）。 Also 'umm, uh, like, so'. English has the same thing, for example when you can't think of a word and just start with 'that, those'.

'Eh, what's that.. that, uh, the name of that function?'

It's pretty easy to mishear it, but 99% of the time you can see from the context that they're not just wildly dropping n-bombs..