Is “foment” the same as “ferment”?

People stirring up discord are often described as “fomenting trouble”. If you search for the phrase on the Internet you’ll find, for instance, Indian agents fomenting trouble in Canada and the Russian Kremlin fomenting trouble in Belarus, to pick just two recent
examples.

But quite often, the phrase used in this situation is “fermenting” rather than “fomenting” trouble. This is a less common phrase, but there are still plenty of instances to be found, all over the world, of people fermenting trouble.

Are both phrases correct or do people write “ferment” when they should say “foment”?

The Oxford dictionary’s definition of foment as a transitive verb is :

instigate or stir up (an undesirable or violent sentiment or course of action)

as in for example :

they accused him of fomenting political unrest

The word derives from the Latin word fomentum, meaning a poultice or a lotion. Originally, to foment was to bathe a part of the body with a warm or a medicated lotion.

Ferment as a transitive verb, meanwhile, means :

incite or stir up (trouble or disorder)

as in for example :

the politicians and warlords who are fermenting this chaos

This word derives from the Latin word fermentum meaning yeast.

As you can see, both foment and ferment have ended up meaning more or less the same thing in this context, despite their different derivations. Perhaps this is because they sound so similar or it might be because they share that sense of heat. Fomentum itself derived from the Latin verb fovere to heat, while fermentum derived from fervere, to boil.

So, while it is more common to “foment” trouble, it is also perfectly acceptable to “ferment” it.