the compound "weapons-grade" is a modern formation, originating in the mid-20th century within the context of nuclear technology and arms control. the first element, "weapon," traces back to old english 'wǣpen', a general term for an instrument of combat, which itself has proto-germanic origins. the connecting 's' functions as a genitive or associative marker, common in english compound adjectives. the second element, "grade," derives from latin 'gradus', meaning a step or degree, entering english via french. the term's literal logic, "of the degree or quality suitable for weapons," directly reflects its specific technical application to materials like plutonium or uranium that meet the stringent purity and potency standards required for constructing nuclear warheads.

Structure: weapon + s + grade weapon (from old english 'wǣpen', meaning an instrument for fighting); s (genitive or attributive suffix from old english, indicating possession or association); grade (from latin 'gradus', meaning a step, degree, or level).