I IS FOR...
ID'N 'EE - Isn't he.

INDERZIDE
- Underside

INJIN' - Engine

INNERDS - One's internal organs An example of how these could be used: "Ees master fer takin' abroad 'th innerds of 'th ole injin', id'n 'ee? 'Ee loves getting' all thikky bits out specially inderzide. Then if 'ees lucky, they all go's back again in a proper manner".
We're sure there are many more so if you know any Devon Dialect words beginning with the letter I, drop John an email;
[email protected]