FWP:
For background see S. R. Faruqi's choices. This verse is NOT one of his choices. I found it interesting and have added it myself. For more on Ghalib's unpublished verses, see the discussion in {4,8x}.
On this ghazal as a kind of unlabeled verse-sequence, see {37,1}. On the macaronic structure of this ghazal, with its Persian first lines and Urdu second lines, see {37,2}.
What does it mean to be one who has been tyrannized over, or oppressed, by 'back-returning'? Such a person could conceivably be one who has done a lot of retreating or back-returning himself (out of cowardice? out of weakness? out of some other dire necessity?). Or more probably, he could be one who has suffered from someone else's cruel reneging or 'back-returning', as the lover has often suffered from that of the beloved (see {14,7} for a classic example).
The 'speech of those with speech brought to their lips' seems to allude to a situation in which people are on the verge of speaking, but the speech hasn't actually emerged from their lips. There's nothing in the grammar of the line to suggest that the speech won't emerge. But of course the juxtaposition with the first line makes the prognosis grimly clear. The speech is destined not to be uttered: instead of emerging, it 'back-returns' or retreats.
If the speaker 'is' such speech, then of course he's intimately familiar with the cruelty of such suppression. Perhaps he's familiar, as a 'stranger' or 'wretch', with the need to suppress his own complaints, demands, protests against injustice, etc.
Or else, as a 'stranger' or 'wretch', he's familiar with the treachery and fickleness of others (local people? beautiful beloveds?) who prove themselves radically and cruelly untrustworthy. If they speak at all, then even as he hangs on their words, they go back on them. If they don't even bother to speak, then he has the agony of watching (what might be) the longed-for words trembling on their lips, unspoken.
Or else 'those' are strangers and wretches, sufferers and
lovers, like the speaker himself, people who often have to cruelly and painfully 'swallow'
their own (unspoken or even spoken) words.
Asi:
I am a traveler, but the kind of traveler who has emerged from the limits/borders of coming back [Asi's text has ;Gariib-e badar-jastah], as if I am that utterance of the speakers' that has come as far as the lip and come out. And it's obvious that an utterance that has come to the lips [and been spoken] cannot come back.
== Asi, p. 65