The wise old saying reminds us that appearances are deceptive.

deceptive 是形容词，由动词 deceive（欺骗）加上后缀 -tive 构成。deceive 来自拉丁语 decipere，意思是"欺骗、蒙骗"。后缀 -tive 表示"具有...性质的"，所以 deceptive 意思是"具有欺骗性的"、"容易误导人的"。