The phrase "of a truth" is an idiom that means the same as "in truth," "in reality," or "indeed." These synonyms are often used to convey the sense of certainty or conviction that comes with knowing something to be true. Other similar terms include "honestly," "truly," "genuinely," and "sincerely." These synonyms are commonly used in speech and writing to emphasize the veracity or sincerity of a statement. Whether used in a formal context or in everyday conversation, these synonyms can help to convey a sense of truth and honesty in communication.