The idiom "一干二净" is formed through a classic Chinese rhetorical structure that pairs numerals with synonymous adjectives for emphatic effect. Literally, "一干" (yī gān) means "one part dry" and "二净" (èr jìng) means "two parts clean," using the numbers "一" and "二" not mathematically but as a stylistic device to create a compound meaning. Together, the two parallel phrases reinforce the same core idea of absolute absence or thoroughness, resulting in a figurative meaning of "completely clean" or "without a trace," often used to describe something being totally finished, consumed, or erased.