The first Mishna in Massekhet Gittin opens with the rule that a person who is a messenger to bring a bill of divorce – a geṭ – from a community in the Diaspora to Israel must be able to attest that the document was written and signed in his presence. Most of the rishonim (including the Ritva, Ramban, and Ran) explain that the massekhet begins with this rule rather than with the basic halakhot of giṭṭin because it is a rabbinic enactment, and the sages preferred to open with a rabbinic enactment – which was close to their hearts – rather than a biblical law, which they will get to later in the massekhet. Another suggestion is that the sages preferred not to begin with a discussion of the dissolution of a marriage, which is a disturbing topic, and chose instead to focus on an enactment that was made to protect the woman from a contested divorce.
The popular term for a divorce document – a geṭ (and, in plural, giṭṭin) – is not a word with a biblical, or even a Hebrew source. It is apparently borrowed from the Syriac gitetu, which means a contract or document of any sort. From the Syriac the word became widely used in neighboring languages, including Hebrew and Aramaic. In the Talmud the word is used by the sages both in its original meaning – a contract of any sort – as well as the specific sefer keritut – a contract given by a man to his wife to end their marital relationship and effect a divorce.
The unusual origins of the word have led the commentaries to suggest a wide range of explanations for its source, including a reference to a midrash that there is a rock in the ocean that is called Gata which has the power to keep other stones from approaching it, and the point that nowhere in the written Torah do we find the letters gimmel and tet (which are the two letters that make up the word get) juxtaposed – a fact that points to the separation that accompanies divorce.