Old English Genesis, first book of the Pentateuch, which tells among other things of the creation of the world, from Latin genesis "generation, nativity," in Late Latin taken as the title of first book of the Old Testament, from Greek genesis "origin, creation, generation," from gignesthai "to be born," related to genos "race, birth, descent" (from PIE root *gene- "give birth, beget," with derivatives referring to procreation and familial and tribal groups).
Greek translators used the word as the title of the biblical book, rendering Hebrew bereshith, literally "in the beginning," which was the first word of the text, taken as its title. Extended sense of "origin, creation" first recorded in English c. 1600.