Funcation names, some are HasFun(), while others are has_fun()

Why are some functions named CamelCase while others are camel_case?

example:
    // Whether the underlying channel is using SSL
    bool is_ssl() const;
    
    // Resets the Controller to its initial state so that it may be reused in
    // a new call.  Must NOT be called while an RPC is in progress.
void Reset() { InternalReset(false); }