Quelch is a relatively uncommon word that means "to suppress, stifle or extinguish." Its antonyms, however, are familiar ones that convey the opposite sense of allowing, encouraging, or augmenting: "kindle," "ignite," "fuel," "stoke," "inflame," "incite," "boost," "stimulate," "provoke," "organize," "cultivate," "foster." In short, the antonyms of quelch all denote actions that incite, encourage or invigorate, rather than suppress or extinguish. They are synonyms of words like "encourage," "promote," or "foment," which denote constructive activities that enable growth, development or progress, and are often associated with positive reinforcement.