I did rather come to feel when I was working in S Wales, that a lot of 'Welsh' technical terms are really only alternative spellings of English words, and terms like 'incline' and 'level' in the above list tend to confirm that.
The same comment applies, to a fair extent, to modern languages like French, Italian and Russian.
The 'Cornish' list seems to me, to contain quite a few terms I have heard in a wide range of areas, under varying spellings - 'pare', for example, for a gang of men ( by implication, working on a price or piecework contract of some sort )
I never heard a word of Cornish spoken in my Camborne days, which included working at Geevor and Wheal Jane at various times. If I were a cynical soul, which heaven forfend 😮 I would suspect that the whole 'Cornish kilt' thing was one of those things people get up to when they really don't have anything more useful to occupy themselves with.
''the stopes soared beyond the range of our caplamps' - David Bick...... How times change .... oh, I don't know, I've still got a lamp like that.