Red flannel was thought to be especially effective, on some sort of colour therapy principle, no doubt.

...and good for flagging down trains with, if your name is Roberta Faraday......

] However, this is not to be confused with hot flannel, a drink of gin and beer, heated after the addition of sugar and nutmeg (current in JA's time).

Also not to be confused with the modern British usage of flannel, to mean a facecloth.

Nor with the colloquial habit of flanneling so as to obscure one's meaning (don't know if this was current in JA's time)..

Nor yet with flummery, which is both a hot drink and fancy talk that signifies nothing.