The phrase "builded a fire under" commonly means to motivate or inspire someone to take action. Some antonyms for this phrase include "dissuade," "discourage," "dampen," and "demotivate." These words suggest the opposite of building a fire, extinguishing or diminishing it. Other antonyms may include "inhibit," "hinder," "restrict," and "restrain," all indicating factors that limit or obstruct progress or drive. Using these antonyms in opposition to "building a fire under" can help provide a broader understanding of the various circumstances and emotions that can sway motivation and momentum.