Ain't is a contraction for
am not,
is not,
are not,
has not, and
have not in the common English language
vernacular. In some dialects
ain't is also used as a contraction of
do not,
does not, and
did not. The development of
ain't for the various forms of
to be not,
to have not, and
to do not occurred independently, at different times. The usage of
ain't for the forms of
to be not was established by the mid-18th century, and for the forms of
to have not by the early 19th century.