Recently someone used the word abrew, as in something is brewing. Is this simply coined on analogy with afoot, or has this word any antecedents? The OED doesn’t show anything for it. I am sure I’ve heard

it’s abrewin’

Not listed in any of my references except for the Great Oracle at Google. I’m sure someone will be a’comin’ with more to add.

Check in OED under a, prefix for the practice of placing a- before verbs, nouns, etc.

The entry under a, particle may be of relevance too, although I’m uncertain of that.

I think that a brewing is simply a non-standard periphrastic verbal form: BE + a + V + -ing, e.g., “time’s a wasting”. I wonder if the a is a reduced form of on, of, or suchlike. It might be connected with the obsolescing (BE + V + -ing) progressive passive, as in “Wheat is selling for 5 cents more a bushel than yesterday” vs “wheat is being sold for 5 cents more a bushel than yesterday”. I’m hoping that Languagehat will know.

This is about the adjective abrew, not the verbal form abrewing.  It doesn’t seem to be in any dictionaries, but that just means it hasn’t been attested often enough to seem worth spending lexicographers’ time and effort to include.  It’s a perfectly good word, if you ask me, since it’s well formed and instantly understandable, and I imagine it’s cropped up every once in a while (as for instance here: “Something new abrew at Gil’s.” It’s an instance of the prefix a- as described by the OED thus:

2. ME. a-: OE. an, on, prep. See A prep.1 above. With nouns, in, on, engaged in, at, in loose combinations, which are really two words; as abed, ashore, afield, asleep, alive. With verbs, adverbs, and prepositions, more closely combined both in form and sense, as aknow, ashame, afore, among, across.

not the verbal form abrewing

Ah, sorry about that. I get to thinking about something, and I ignore the obvious in a post.

Well, I’ll admit it’s easy to guess what might be meant by “abrew”. “Something’s [a]brewing” > “something’s abrew”, I suppose.

If it seems reasonable, what about these? (I think it’s easy enough to guess what each of these must mean.)

// The railroad strike is over; the trains are arun again.

// My broken leg is healed; I’m awalk again.

// Something’s acook!

// Hurry up, time’s afly!

// This neologism is astink!

I agree that none of those seem likely to catch on.

“Abrew” does not offend the ear as much as those, possibly because it is more reminiscent of the familiar “aboil”.  In some metaphorical uses the two terms would be nearly interchangeable, and I wonder if in fact “abrew” may have orginated as an error for “aboil”.

Maybe those words offend because they’re all formed from intransitive verbs, whereas “brew” is transitive?

"Brew”, like “boil” and “cook”, can be used either transitively or intransitively.  “Abrew” to me suggests the intranstive form, as it happens.  (Something is brewing.)

This neologism is astink!

It is a mistake to think that if one can make up a form that 1) seems to the creator to be parallel to another form and 2) is clearly unacceptable, then the allegedly parallel word is also unacceptable.  (Tomorning is wrong, therefore today must be wrong too.) It doesn’t work that way.  Every word gets judged on its own merits, and that judgment is done not by thee or me, or by (perish the thought) an Academy, but by the collective judgment of the speakers of English.  I think abrew is fine, you don’t like it.  So what?  The more people use it, the more of a word it is, regardless of individual preferences.