Hittite is closest to the root of Indo-european languagues.

The term Indo-Hittite was proposed by scholars who believed that Hittite and the other closely related Anatolian languages represented a language branch coordinate with all the other Indo-European languages combined, rather than forming another branch coordinate with the individual Indo-European branches (Celtic, Germanic, etc.). In other words, they proposed that at one time there existed a protolanguage (Indo-Hittite) that split into two branches, Anatolian and Indo-European (from which the various branches of Indo-European later evolved). Most scholars, however, consider the Anatolian languages, including Hittite, to be simply a branch of Indo-European.