Tomos

The word tomos is a word related to the word tome (a large volume/book) which is of Greek origin that means a cutting and is derived from the word temnein meaning to cut/slice.

Tomos as used in the Orthodox Christian Church denotes a small book that contains an announcement or similar text: such as the “TOMOS of Alexis, by the Mercy of God Patriarch of Moscow and All Russia” that granted autocephaly the Orthodox Church in America.

Source

Any good dictionary (Tome)