The word "有恃无恐" is formed by sequentially combining four characters: 有 (have), 恃 (reliance), 无 (without), and 恐 (fear). It structurally pairs "有恃" (having reliance) with "无恐" (without fear), creating a direct cause-and-effect relationship where the possession of a support leads to the absence of fear, thus constituting the idiom's meaning.