Deuteronomy

The title Deuteronomy is derived from Deuteronomy 17:18, where the Greek LXX translated δευτερονόμιον (deuteronomion, meaning “second law”), for the Hebrew מִשְׁנֵ֨ה הַתֹּורָ֤ה (mishneh haTorah), meaning “a second Torah / law” (commonly translated as “a copy of the law”).

Deuteronomy 17:18 (ENGLXXUP), emphasis added

And when he shall be established in his government, then shall he write for himself this repetition of the law into a book by the hands of the priests the Levites….