FWP:
SETS == IDIOMS; INEXPRESSIBILITY
SPEAKING: {14,4}
A small mouth is a sign of beauty, so naturally the beloved's mouth is the smallest one possible-- or impossible. In fact her mouth is vanishingly small, so that it hardly exists. This idea is played on to witty effect in {24,7}, and also just two verses along in the present ghazal, in {91,4}.
Thus 'With what mouth should/would one express thanks?' here idiomatically means something like, 'How can thanks ever be sufficiently expressed?'-- but literally of course asks what mouth one might or should use to express thanks. As S. R. Faruqi points out (May 2003), it suggests that the speaker both does (because of the idiomatic force of the expression), and doesn't (because he doesn't seem to have a mouth available), express thanks.
Compare the use of the same idiom in {161,10}, where it means 'how would one have the nerve to...?'. Might there be overtones of that usage here as well? Since the beloved is emphasizing the expression of meaning without speech, perhaps it would be inappropriate, or even insolent, to have the gall to express one's gratitude in words? See {152,3} for more discussion of such 'foot of' idioms.
Along slightly different lines, the verse invites us to contemplate the beloved and her vanishingly small mouth. It seems that she asks after the lover, somehow-- yet she doesn't say anything, she doesn't use speech. To convey her non-speaking, the lover chooses another idiomatic phrase, paa-e su;xan darmiyaa;N nahii;N , that means 'nothing was said', or 'no conversation took place'. For another example of this 'foot-between' idiom, see {91,13x}.
But if we take the elements of this phrase literally, they imply that mere speech is vulgar, bothersome, and intrusive. If the 'foot of speech' is not 'in between' the lover and beloved, then they are alone together without barriers-- and what could be better than that? Except, of course, that she won't talk to him. This verse reminds me of {14,4}, in which the lover proudly boasts that even if he can't fathom her secrets and in fact can't understand a word she says, still, it's no small thing that she's 'opened up' to him. Or rather, he doesn't necessarily assert it. Thanks to the wonderful multivalence of kyaa, he may also be asking, 'Is it a small thing?'.
And here too, the lover doesn't assert the beloved's kindness, but instead asks, how can I express appropriate gratitude for this 'special kindness'? Ghalib is making his usual clever use of inshaa))iyah speech, such that what looks at first like a rhetorical question ('How can I thank her enough?') in fact turns, as we consider the verse, into a genuine question: well, for someone who won't ask about you in mere words, what is the appropriate way to express gratitude? Surely not with anything so vulgar as words, from anything so commonplace as a mouth? Perhaps the thanks should be as ineffable (and suppositional) as the inquiry itself. Perhaps it should be a mere look, or a slightly raised eyebrow?
In short, it seems, sadly but not surprisingly, that the beloved has probably not inquired after the lover at all. The lover is-- just as in the previous verse, {91,1}, and so many others-- trying desperately to put the best face possible on the painful facts of the case. His convoluted rhetoric itself creates the implication; it itself is the very thing that lets us see behind it.
Compare Mir's use of the same 'foot' idiom: M{1624,3}.
Nazm:
It's the account of a coquetry of the beloved's-- she doesn't speak to me, but she always seeks to find out how I am. And this aspect too emerges, that the author may have composed this verse as a ;hamd . (89)
== Nazm page 89