/haʊ̯ əm aɪ̯/ → /haʊ̯ m‿aɪ̯/
From how'm + I, so a contraction of how am I, phonetically respelled as if it were how + my.
how my
- (nonstandard, colloquial) Contraction of how am I.
- The regular spelling of how'm I is more common.
1931 June, Town Journal[1], volume 38, Farm Journal, page 30:Aw, how'my gonna make m'livin' robbin' banks 'n bumpin' a feller off occas'nally?
1984, Stephen Dixon, Time to Go[2], Johns Hopkins University Press, →ISBN, page 141:I hang up. "How my going to get to sleep tonight, Mag? How my going to?"
2013, Andy Bloch, Rooster Mitchell, The Killer and the Comic[3], Original Works, →ISBN:So how's he gonna' find me? How my gonna' find him?