Dogmatic assertions proceeding from this or that philologist are common enough.

Trustworthy results are correspondingly scarce.

One instance may be cited in illustration.

It has been argued that the name 'Kent' is derived from the Celtic 'Cantion', and not from the Latin 'Cantium', because, according to the rules of Vulgar Latin, 'Cantium' would have been pronounced 'Cantsium' in the fifth century, when the Saxons may be supposed to have learnt the name.

That is, Celtic was spoken in Kent about 450.