The following book remains to this day, one of the most influential books for understanding grammar in the Gaelic language. It is native to the Gaels of Scotland. As a Goidelic language, Scottish Gaelic, as well as both Irish and Manx, developed out of Old Irish. It became a distinct spoken language sometime in the 13th century in the Middle Irish period, although a common literary language was shared by Gaels in both Ireland and Scotland down to the 16th century. Most of modern Scotland was once Gaelic-speaking, as evidenced especially by Gaelic-language place names.