A sexual overtone can be sensed here! It is an obscene pun playing with the similarity in pronunciation between the first syllables of the word and the slang for female genitalia, 'cunt'.

This pun is also present in Shakespeare's Hamlet, when Hamlet to innocent Ophelia says, 'Do you think I meant country matters?'

Pun: a humorous use of a word in such a way as to suggest two or more of its meanings or the meaning of another word similar in sound. (definition from Merriam Webster)

Source: Book: John Donne, The Complete English Poet (1971)

It's unclear why for the moment, but there are several references to death here. See"grave", "smaller than life", "undertake", "retire", "weary long time", "mortal". My initial guess is that Seegrave will be witness to a death given the pun on his name. As for Cuff, it remains to be seen what role he will have in the story, but this passage does hint at some entanglement with death at some point.

Hilarity aside, it's interesting that Franklin makes such an obvious pun at Betteredge's name. Is this simply a wink and a nudge from Collins, or is he trying to hint that the character names carry some meaning? Alternatively, could it be that Betteredge is actually a bumbling buffoon who has no clue of what's going on? This pun serves to remind the reader to keep an eye out for clues and double meanings that may be hidden within the lines.

While she may disagree with him in other places, this sounds like a statement where the two are in Lockestep (please forgive me.)

a pun on "morning". John Donne is forbidding the morning from coming so that he does not have to leave as well as forbidding his lover from mourning his departure and possible death.