If you tell us what they say instead then I can probably give you some insight. There's "bovvered" or there's "what da hell" or there's "fankyou"... I can pro

If you tell us what they say instead then I can probably give you some insight. There's "bovvered" or there's "what da hell" or there's "fankyou"... I can probably think of several more dialects where "th" is replaced with something else.