An accessory is a small item that adds some beauty or convenience to its father item. For example, a mobile phone case is an important accessory protecting your smart phone. A bracelet or a watch is also an accessory, adding some charm to the person wearing it.
The French word "accessoire" has a lot in common with the English word access. Each accessory makes eadier access to its wearer. For example, to access music in your smart phone you should buy earphones, an important listening accesdoire.