all the modern brythonic languages (breton, cornish, welsh) are generally considered to derive from a common ancestral language termed "brittonic", "british", "common brythonic", "old brythonic" or "proto-brythonic", which is thought to have developed from proto-celtic or early insular celtic by the 6th century ad. brythonic languages were probably spoken before the roman invasion at least in the majority of great britain south of the rivers forth and clyde, though the isle of man later had a goidelic language, manx. northern scotland mainly spoke pritennic, which became pictish, which may have been a brythonic language. during the period of the roman occupation of southern britain (ad 43 to c. 410), common brythonic borrowed a large stock of latin words. approximately 800 of these latin loan-words have survived in the three modern brythonic languages. "romano-british" is the name for the latinised form of the language used by roman authors.