Ever wondered about the phrase “how come”?  I’ve always wondered how it became a common phrase since it sounds like it makes no sense.

I looked it up and this is what randomhouse.com came up with:

The admittedly obscure-looking how come?, a colloquial Americanism for ‘how is it that?’ or ‘why?’, is based on a shortened form of an expression such as “how comes it that…” or “how did it come about (that)…”

These still-somewhat-obscure phrases depend on a usually archaic sense of come meaning ‘to come about; happen; occur; become’, combined with an archaic word order placing “how” and “come” together at the beginning of a sentence.

While this type of use seems rare now, it was once very common. A selection of examples showing this earlier use of how with come (not the same as our modern colloquial phrase) (some of this examples show slightly different structures, such as the Austen quote, which is “come about” in an archaic word-order):

“How comes it then that he is prince of devils?” (Marlowe, Doctor Faustus); “How comes it that they travel?” (Shakespeare, Hamlet); “How comes it thus?” (Milton, Paradise Lost); “How comes any particular thing to be of this or that sort?” (John Locke, An Essay Concerning Human Understanding); “How comes it to be any concern of yours?” (Fielding, Tom Jones); “How comes this about; there must be some mistake” (Jane Austen, Mansfield Park); “How comes it that we whalemen of America now outnumber all the rest of the banded whalemen in the world?” (Melville, Moby-Dick); and “Then if it’s so precious how comes it to be cheap?” (Henry James, The Golden Bowl).The American sense is derived from uses like these, and as the original phrase “how comes it…” has become difficult to understand, the expression how come has become more and more a set phrase.

As we’re familiar with it, how come first appears in John Bartlett’s 1848 Dictionary of Americanisms, one of the important early books dealing with American slang and colloquial expressions. Bartlett’s comments suggest that it was in widespread use when he wrote.