The phrase "whys-wherefores" can be described as the reasons behind something. There are several synonyms for this phrase, including "rationale", "explanation", "justification", "cause", "basis", and "motivation". These words can be used to express the reasons for a decision, action, or situation. For example, a company may provide a rationale for why they chose a particular product or strategy. Similarly, an individual may offer an explanation for their behavior or reasoning. The use of synonyms can add variety and depth to written and spoken language, and can help convey ideas and thoughts in a concise and clear manner.