1. Are you sure you linked to the right page? That looks to be a condiment.

2. Chemical warfare was used before the Romans, for instance, like that condiment, the greeks had it before them. (Though I don't believe the greeks invented it first either). For example, see this wikipedia article (which is really in need of some improvement) https://en.wikipedia.org/wiki/Timeline_of_chemical_warfare

Garum is supposedly similar to south-east Asian fish sauce so as someone who can't stomach even regular seafood, let alone that horrible stuff, I'll stand by their humorous assessment :)