The word 沧海一粟 is formed by directly combining the literal elements 沧海 (cāng hǎi), meaning "vast sea" or "deep blue sea", and 一粟 (yī sù), meaning "one grain of millet", to create a stark, metaphorical contrast where the immense scope of the sea is juxtaposed with the minute scale of a single grain, thereby illustrating the concept of extreme insignificance within a vast context.