I need help explaining this quote from the Miller's Tale.'Now, John, my dear,/My excellent host, swear on your honour here/ Not to repeat a...

As the previous person suggested, the conversation is
between Nicholas, the boarder, and John, the homeowner and old husband to the young and
beautiful Allsion. The plot is correct in which Nicholas and Allison want to engage in
adult activities obviously without John's knowledge.

The
quote itself stems from Nicholas' role in instigating actions that will lead to he and
Allison engaging in the adult activities.

Remember that the
time period and situation in England allows for pretty much anything to be done in the
name of Christ or God. Therefore, because Nicholas uses "Christ" it will assure John
that the issue at hand is "for real!"

The explanation of
the quote is as follows...

"Now John...honour here" = by
addressing him by name, the speaker is being respectful and showing the listener that he
thinks highly of him; then of course he (Nicholas) uses compliments to gain the
attention of John and even goes so far as to ask him to put his honor on the line -
which is a basis for the Code of Chivalry.

"Not to repeat a
syllable ...Shall fall upon you."= Nicholas then tells John not to repeat anything about
the issue at hand (which is going to be Nicholas' prediction of a great flood in the
meterological forecast) but not because Nicholas says, but because Jesus Christ says
(remember, this makes everything more believable due to the "intensity of Christianity
and its press on society").

"You'll be driven mad" = To go
against what Christ says will cause John to be persecuted, tortured, or to "pay for his
sin" which Nicholas tells him is going to be
insanity.

Obviously the role of this quote is to convince
John to abide by the plan that Nicholas (who is a credible source because of his
"scholarly background" and who had been "faking" intense mental breakdown in his room
prior to this conversation).

John then
replies,

"Christ and...lad" = basically John swears to God
and Christ that he will not say anything about the issue at hand because that is what
God wants.

"I'm not given to gab." = John states that he
doesn't gossip or really talk to anyone about random
issues.

"Say what...harrowed hell" = John reiterates to
Nicholas that he can tell him anything he wants, because John will not repeat it to
anyone, man, woman or even child of God/Jesus who basically died for every Christian on
the cross (harrowed hell - took the worst punishment for others
sins).