Looking at two words in a Cornish site and a Czech site I've come across two possible matches which may not mean very much.
Most of the words in the Cornish mining words seem to be a bit general.
However the Czech for 'miner' is 'hornik'. Which sounds a bit like cornish perhaps
Cornish for 'why' is 'prog'. Czech is 'proc' with an accent on the final 'c' giving it a slightly different sound between ts and tchs I think.
http://www.cornwallinfocus.co.uk/language/phrases.phphttp://www.wordbook.cz/index.phpI'll keep digging. There has been a lot of time for both languages to come up with new terms or become influenced by other languages so I imagine the best route to go would be for ancient placenames perhaps or at least placename elements and given the the possibility is that it is miners we are talking about I would assume mining areas may have similarities.
If there is any reason for similarity.