leak-proof

The compound "leak-proof" is a modern English formation following a productive pattern for creating adjectives that describe resistance. The first element, "leak", originates from a common Germanic root related to dripping or seeping, a concept fundamental to its modern meaning. The second element, "proof", has a rich history stemming from the Latin verb probare (to test), which evolved through Old French to signify evidence that withstands testing, and eventually became a suffix denoting imperviousness. The logic of the compound is transparent: it describes an object or system that has been tested or designed to withstand and prevent the action of leaking, seamlessly connecting the literal prevention of seepage to metaphorical applications like information security.

Structure: leak (verb) + proof (adjective suffix) - leak: From Middle Dutch leken or Middle Low German leken, meaning "to drip, leak". A verb root describing the unwanted escape of a substance. - proof: From Old French preuve, prove, and ultimately Latin probare ("to test, prove"). In English, it functions as an adjective-forming suffix meaning "resistant, impervious, able to withstand".