This word comes from the Latin “armamenta,” meaning “implements, weapons.” It was used in English as early as the 1600s to refer to a country’s arsenal of weaponry, but that usage is now obsolete. Around the 1820s, “armamentarium” came back into regular use to refer specifically to the medical equipment and therapeutic techniques available to a practitioner. This was around the time modern medical practices were being developed, and it was becoming more important to have adequate tools and supplies. Only a few decades later, the word was being used to refer to a collection of supplies in general, and that is how “armamentarium” continues to be used. It is a more formal term, but if you’re proud of your equipment and the collection you’ve acquired, it’s only right to call it your armamentarium.