The word 究竟 is formed by combining two independent characters, each contributing core semantic concepts that merge into a new, abstract meaning. 究 originally conveys the idea of "investigating to the end" or probing deeply into a matter, while 竟 carries the sense of "completion" or "finality". Together, they create a compound that conceptually represents "reaching the ultimate end-point of an inquiry", which evolved to express the notion of "the actual truth" or "the final outcome" underlying a situation.