Origin: Latin suffix -ary
Accessary has 4 different meanings across 2 categories:
Someone who accedes to some act, now especially a crime; one who contributes as an assistant or instigator to the commission of an offense.
Accompanying as a subordinate; additional; accessory; especially, uniting in, or contributing to, a crime, but not as chief actor. See accessory.
The word comes from Medieval Latin accessārius via Middle English. It originally meant something that is added or attached to a main thing.