Old Welsh is a member of (insular) Celtic branch of the Indo-European language family.

Its first attestations come from short texts from the end of the 8th century AD. It was in use until the 12th century. However, its corpus is rather limited, without an example of adjective valence.

Bibliography:

Fortson, Benjamin W. 2009. Indo-European Languauge and Culture: An Introduction. John Wiley and Sons, p. 330.

Willis, David. 2010. Old and Middle Welsh. In: Martin J. Ball and Nicole Müller (eds.), The Celtic languages, 117-160. London – New York: Routledge.