Don't know this is accepted translation. But among Native American there is a thing called "medicine bag". This is used as tarisman of protection against evil spirits, and its contents differ from a person to another.
"Medicine" in this case does not necessary mean medicinal or cure against diseases, but against eveil spirits.

Now why "ball"? See below.
http://dic.livedoor.com/psearch?key=��
くす‐だま【薬玉】
１ 種々の香料を詰めた錦にしきの袋に薬草や造花をつけ、長い5色の糸を垂らした飾り物。不浄を払い、邪気を避けるものとして、端午の節句に柱などに飾った。中国の風習が輸入されたもの。くすりの玉。続命縷しょくめいる。長命縷。《季 夏》「―の人うち映えてゆききかな／虚子」 ２ 造花などで１に似せて作った飾り物の玉。式典・祝い事などに用い、割ると中からハトや紙吹雪が出るものもある。

So you know "kusudama = kusuri no tama" = 長命縷, thus mecicine ball.
For this, "tarisman ball" could be your another choice.