The word 不可思议 is formed through a conceptual fusion drawn from ancient Buddhist philosophy, where 不可 means "cannot" or "must not", 思 means "to think" or "conceive", and 议 means "to discuss" or "comment upon". It originated to describe the profound, ineffable nature of enlightenment or sacred truths, which were considered so transcendent that they lay beyond the limits of human intellectual reasoning and verbal expression. Thus, the term coalesces into a single idea capturing that which is so astonishing, mysterious, or sublime that it defies and transcends the ordinary processes of the human mind and speech.