We know how they called their own language: "nešili", while they called "hattili" the language of the previous Non-Indo-European inhabitants of the place where the capital of the Hittite Empire was located. The "hattili" language does not have any certain affinities with other known languages, but it has some resemblances with certain North-Caucasian languages.
So the Hittites would better be called something like "Nessites".
Thus our name comes actually from the name of the people conquered by them (Hatti).
While the Hittites were originally identified with the people mentioned in the Bible, it is also possible that some or all of the references from the Bible are not to what we call Hittites, but to some "Hatti" people.
The Bible does not refer to the Hittite Empire but only to some people of Hittite origin that are encountered in the present territory of Israel, so they could have very well been of Hatti origin.