No pythons native to the British Isles, but they do have adders (not abundant, but not to be messed with). Also trewser snakes, but that's a different story...
The Irish for the adder type of snake is "nathair", from the Old Irish "nathir". Don't know if it's ever been used as a personal name, but if you insist, I'd opt for the older version (less likely to be pronounced "gnat-hair").
As to pronunciation, ask Phyllis on this board.
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