Cornish and Breton in southwestern Britain and Brittany, and Cumbric in northern Britain. Kenneth H. Jackson concluded that the majority of the changes that transformed British into Primitive Welsh belong to the period from the middle of the 5th to the end of the 6th century. This involved syncope and the loss of final syllables. If the poem dates to this time, it would have originated in an early form of Cumbric, the usual name for the Brittonic speech of the Hen Ogledd. Jackson suggested the name "Primitive Cumbric" for the dialect spoken at the time. Sweetser gives the example of the name Cynfelyn found in Y Gododdin; in British this would have been Cunobelinos. The middle unstressed o and the final unstressed os have been lost. Ifor Williams, whose 1938 text laid the foundations for modern scholarly study of the poetry, considered that part of it could be regarded as being of likely late 6th-century origin. This would have been orally transmitted for a period before being written down. Dillon cast doubt on the date of composition, arguing that it is unlikely that by the end of the 6th century Primitive Welsh would have developed into a language "not notably earlier than that of the ninth century". He suggests that the poetry may have been composed in the 9th century on traditional themes and attributed to Aneirin. Jackson however considers that there is "no real substance" in these arguments, and points out that the poetry would have been transmitted orally for a long period before being written down, and would have been modernised by reciters, and that there is in any case nothing in the language used which would rule out a date around 600. Koch suggests a rather earlier date, about 570, and also suggests that the poem may have existed in written form by the 7th century, much earlier than usually thought. Koch, reviewing the arguments about the date of the poetry in 1997, states: Koch himself believes that a considerable part of the poem can be dated to the 6th century. Greene in 1971 considered that the language of the poem was 9th-century rather than 6th-century, and Isaac, writing in 1999, stated that the linguistic evidence did not necessitate dating the poem as a whole before the 9th or 10th century. The other approach to dating the poetry has been to look at it from a