בראשית

Where it comes from

A prepositional phrase בְּ־ (b'-, “in”) + רֵאשִׁית (reshít, “beginning”) that appears to be unsuitable in the context of Genesis 1, which recounts the creation and beginning of the universe, as it lacks the definite article and thus literally translates to "in (a) beginning", instead of the expected "in the beginning". This already troubled early rabbinic commentators, such as Rashi, and led some modern scholars to suggest that the Tiberian vocalization might be incorrect and that the first verse of Genesis is a mere adverbial phrase of the following verse, reinterpreting רֵאשִׁית to be in the construct state and בָּרָא in the infinitive construct: בְּרֵאשִׁית בְּרֹא אֱלֹהִים אֵת הַשָּׁמַיִם וְאֵת הָאָרֶץ׃ (“When God began to create the heaven and the earth”). This interpretation, however, directly conflicts with all early translations of the Torah that are still extant, namely the Greek ones found in the Hexapla of Origen, or the Aramaic Targumim, most of which were executed by people who experienced Hebrew as a living language. The most reasonable solution may be to assume that the Hebrew speakers simply felt no need to specifically denote this word as definite, as everything only has one beginning by nature. Alternatively, this wording may have been in some way idiomatic, with a meaning more or less tantamount to "in the beginning", such as "initially", or "firstly".

As all the other books of the Torah, Genesis in Hebrew is named after its first occuring word.