Israelian Hebrew (or IH) is a proposed northern dialect of biblical Hebrew (BH). It is proposed as an explanation for various irregular linguistic features of the Masoretic Text (MT) of the Hebrew Bible. It competes with the alternative explanation that such features are Aramaisms, indicative either of late dates of composition, or of editorial emendations. Although IH is not a new proposal, it only started gaining ground as a challenge to older arguments to late dates for some biblical texts since about a decade before the turn of the 21st century: linguistic variation in the Hebrew Bible might be better explained by synchronic rather than diachronic linguistics, meaning various biblical texts could be significantly older than many 20th century scholars supposed.
What constitutes linguistic irregularity in the MT is not in dispute, nor is the affinity of many these features to aspects of Aramaic. What distinguishes the theories is a historical question of language contact. It is known that the southern kingdom of ancient Israel, Judah (from which name the Jewish people are known), suffered a defeat at the hands of the Aramaic speaking Babylonians, which involved deportation according to standard Babylonian practice. This language contact is recognised by all scholars, as are the resultant Aramaisms in Late Biblical Hebrew (LBH). What the IH proposal explains, which LBH does not, is the Aramaisms (and other features) that appear in texts that many scholars would consider antedated the period of exile in Babylon. The two theories are thus not incompatible, which is why they co-existed throughout the 20th century. However, the more recent work does pose a challenge to the traditional dating of some specific texts in the Bible, the Song of Songs in particular.