So how come we say “how come?”, and is it current in all English speaking countries? And if it is current in your dialect, is it considered appropriate in all contexts, or only some?
Actually, the etymology can be easily imagined. “Come” in this phrase could be a past participle, so it might have been something like the following:
“How has it come that…”
But even if it is an infinitive, it could as well be,
“How did it come that…”
How far back is the phrase attested?
I’ve often wondered the same quesstion, but wouldn’t the etymology be more like “how has it come to be that…”?
The OED attests “How come” as far back as 1548. Shakespeare used it in “Coriolanus.”
I always figured it was short for something like “how have you come to this conclusion/course of action/etc.”. No cites tho’.
I agree. ‘How comes it that…?’
“It occurs in writing that imitates conversation but is not usual in Edited English and may be a contraction of How does it come about that . . .” (from The Columbia Guide to Standard American English)
These things change over time and some words that sound similar to modern English definitely do not mean the same as the modern usage. Take the example of the balcony scene in Romeo and Juliet. Wherefore means basically the same as why, and has nothing to do with location.