bombproof

the word is a modern english compound, formed by directly combining two existing english words. "bomb" entered english in the 17th century from french, tracing back to the latin "bombus" for a deep, hollow sound, which itself is onomatopoeic from greek "bombos." "proof" derives from the latin verb "probare," meaning to test or demonstrate the goodness of something, which entered english via old french. the compound "bombproof" logically follows the pattern of "proof" as a suffix meaning "impervious to," creating a term whose literal meaning (resistant to bombs) naturally extended metaphorically to describe anything considered extremely safe or fail-safe.

Structure: bomb + proof bomb (from latin bombus, a booming sound, via french bombe; the explosive device). proof (from latin probare meaning to test or prove, via old french preuve; here meaning resistant to or able to withstand).