So "ain't" is a contraction of "am not" but how? Other contractions like "don't" "isn't" and "can't" all make sense. But how do you get 'am' from 'ai'? Same question for won't how did we get 'wo' from 'will'?
Amn't dates to 1618, and after a little while it was shortened to
an't. In non-rhotic dialects (that is, dialects that drop /r/ after vowels),
an't was also used for
are not (though I assume they were pronounced a little differently). Meanwhile,
in't and even
en't were sometimes used for
isn't, and then
an't began to be used for all three. It's not clear to me how or why the vowel changed to the long
a sound in
ain't, but presumably it was spelled this way to reflect that change.
A similar change happened with
hasn't >
han't >
hain't. Then, since some English dialects drop initial /h/, it became homophonous with
ain't, so now
ain't also covers
has not. Some dialects even have
cain't for
can't, so there must be something that explains the vowel change in all three. I'm just not sure what it is.
I'll get to
won't and other weird contractions tomorrow.