BCC is the initial ticker used or preferred by its team or by the community. When you are aware of the happenings when they insist on splitting Bitcoin's chain and called the new coin as "Bitcoin Cash" some used the ticker BCC for it and some uses BCH. And now, the official ticker of BitcoinCash is BCH. If you happen to encounter BCC/BCH, they are the same  thing but it is best to verify it first.