What does accessary mean?
The definition of accessary
Ac*ces”sa*ry (#; 277), a.
Accompanying, as a subordinate; additional; accessory; esp., uniting in, or contributing to, a crime, but not as chief actor. See Accessory. To both their deaths thou shalt be accessary. Shak. Amongst many secondary and accessary causes that support monarchy, these are not of least reckoning. Milton.
Ac*ces”sa*ry (277), n.; pl. Accessaries.
Etym: [Cf. Accessory and LL. accessarius.] (Law)

One who, not being present, contributes as an assistant or instigator to the commission of an offense. Accessary before the fact (Law), one who commands or counsels an offense, not being present at its commission.

— Accessary after the fact, one who, after an offense, assists or shelters the offender, not being present at the commission of the offense.
Note: This word, as used in law, is spelt accessory by Blackstone and many others; but in this sense is spelt accessary by Bouvier, Burrill, Burns, Whishaw, Dane, and the Penny Cyclopedia; while in other senses it is spelt accessory. In recent text-books on criminal law the distinction is not preserved, the spelling being either accessary or accessory.