It's not as straight forward as it might seem. The en- and the -col- seem obvious enough, but the -polate has more in its history than meets the eye. It would seem to be derived from extra- or interpolate and, indeed, the root for this -polate goes back to the IE root pel- meaning to thrust, strike, drive. Unfortunately, by the time this root got to interpolate it had come to mean fulled (of cloth). Interpolate came from the Latin interpolis or interpolus, refurbished.