1942, American English, in reference to movement within the same country (as distinguished from immigration), from in (prep.) + migration.
inlier
inlighten
inline
inly
inmate
in-migration
inmost
inn
innards
innate
inner
)window.location='https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=byronic106@yahoo.com&lc=US&item_name=Donation+to +Help+Keep+Etymonline+Free+and+Open&no_note=0&cn=&curency_code=USD&bn=PP-DonationsBF:btn_donateCC_LG.gif:NonHosted'){kind=link}