On Mon, 28 Jan 2019 21:24:51 +0800, Stewart Fraser <[log in to unmask]> wrote:

>The etymology of “only” is “one body”. 

Those are the ultimate meanings of the components.  But modern English _-ly_ = Germanic _-līkaz_ was grammaticalised long ago, as an adjectiviser (NB not a manner adverb formant!  Modern English has innovated there).  And it's probably long ago that it became possible to build new words from it with only the sense of 'like', not the old unbleached sense of 'body'.  

This particular derived word seems to be old itself, given that it's elsewhere in Germanic as well: Danish _enlig_ 'single, solitary', Middle High German _einlich_ 'uniform; consistent'.  To me the common denominator looks like simply 'one-ish', i.e. this was the adjectivisation of 'one' which could specialise in different directions.  I'd bet the English started out similar to the Danish -- "I caught a single solitary fish" -- and then more or less as you sketch.

>So presumeably, originally it only qualified discrete nouns. Presumeably its usage spread from there to uncountable nouns and then to clauses (via situations where marking the noun as “below expectation” had exactly the same meaning as marking the whole clause as “below expectation”). And after that presumably it became possible to qualify a single verb by “only”. That is … no other verbs/action took place.

Or maybe, as Tony said, it just wandered free in the syntax of the sentence, and originally belonged to a noun phrase.  Of the set of potential (say) objects, none other than those enumerated are actually objects.  This, together with the very easy slippage from a potential situation to an expected one (people love to assign normative valence to things), should be the bridge from And's basal meaning 'none other than X has Y; if Y then X' to your scalar 'below expectation' sense.

>The words put forward so far as “opposites of only” I have found unconvincing. (I can go into why, if anybody wants to know). 

I agree with you for most of what was offered, and with your conclusion that English doesn't have an opposite of scalar "only" with both the same degree of naturality and centrality in that meaning.  But I had thought of "no less than" before I saw And suggest it; both that and his "as many as" have exactly the meaning you are asking for as their prototype.  What do you find wrong with them?