A badge worn in mediæval times by those who had recanted their “heretical” opinions. It was designed to show what they merited, but had narrowly escaped. (See Fagots.)
Il y a fagots et fagots. There are divers sorts of fagots; every alike is not the same. The expression is in Molièe's Le Médecin malgré lui, where Sganarelle wants to show that his fagots are better than those of other persons; “Ay, but those fagots are not so good as my fagots.” (Welsh, ffag, that which unites; Anglo-Saxon, fægan, to unite.)
Sentire les fagots. To be heretical; to smack of the fagots. In allusion to the custom of burning heretics by surrounding them with blazing fagots.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894