One of the mysteries of the English language finally explained.
A collection or group of instruments.
Late 19th century; earliest use found in Davenport (Iowa) Tribune. From instrument + -arium, originally after German Instrumentarium collection or group of (in early use, surgical) instruments, itself after post-classical Latin instrumentarium treatise describing and depicting surgical instruments.
In this article we explore how to impress employers with a spot-on CV.