It is assumed that Pictish must once have predominated in the northern Inner Hebrides and Outer Hebrides. The Scottish Gaelic language arrived from Ireland due to the growing influence of the kingdom of Dál Riata from the 6th century AD onwards, and became the dominant language of the southern Hebrides at that time. For a few centuries, the military might of the ' meant that Old Norse was prevalent in the Hebrides. North of , the place names that existed prior to the 9th century have been all but obliterated. The Old Norse name for the Hebrides during the Viking occupation was ', which means "Southern Isles"; in contrast to the "", or "Northern Isles" of Orkney and Shetland.