When describing a problem or issue, it's important to have a variety of ways to express where it originated from. Some synonyms for "source of trouble" include root cause, origin, crux, catalyst, trigger, instigator, and propeller. Each of these words suggests a slightly different nuance to the problem, from the underlying cause to the one event that set everything off. Understanding these small differences in language can help you effectively communicate the problem to others and work towards resolving it. So next time you're trying to pinpoint the "source of trouble," consider using one of these synonyms to bring specificity and clarity to the conversation.