Arnold Zwicky at Language Log points out that the "derivative" of "financial derivatives", a word we've been hearing lots in the news lately, is not derived from the "derivative" of calculus. (This is commenting on a misunderstanding in a recently published letter to the New York Times.)
It never made sense to me that while the verb for "find the integral" is "integrate", the verb for "find the derivative" is "differentiate" -- in one case the forms are parallel and in the other they aren't. Of course the derivative involves finding a difference, but the language seems a bit inconsistent. And I've had the occasional student refer to "derivating" a function.
It probably doesn't help that they both start with d, and that every d-like symbol (off the top of my head, at least d, D, δ, Δ, and ∂) gets used for some sort of derivative/difference-like thing in some context.)