I don’t know how widespread this is, but in Ireland it is very common to hear “if I hadda gone” or possibly “if I had of gone” in place of “if I had gone”. It is used in the negative too, viz., “If she hadn’t a gone”.
I have seen this written exactly once, in an article by an Irish journalist in the Sunday Times, as follows “if he had of known”. But I hear it in spoken language all the time.
It does not occur in straightforward statements about past action such as “I had gone”, only in conditional statements.
Is this usage common outside Ireland? Does anyone know why people say this? I have one idea - that people are actually saying “had have gone” by analogy with other modal constructions such as “should/could/would have gone”.
Like the Italian accent, “that’s a gooda meataballeh!”
In some languages, the tendency is to soften a final hard consonant with a barely pronounced vowel following it. And if that extra vowel is overemphasized, it can become a full blown extra syllable in some dialects.
Another example: professional singers are sometimes taught to continue to voice a vowel through the final consonant, which can make a sung ‘good’ sound as ‘goodeh.’ This is mostly for choral or stage singers who are unamplified, otherwise, consanants can be lost since they are quieter than vowels.
On the other hand, you have some languages and dialects that tend to make the final consanant soft by dropping it altogether. “Wha a goo boy!”
I think what’s happening is, an original “if I would have gone” was contracted to “if I’d a’ gone” which was misheard as “if I had of gone” which was contracted to “if I hadda gone.”