Senses
狗嘴里吐不出象牙/ 狗嘴裡吐不出象牙 nothing nice comes from a filthy mouth
A mean person never has a good word to say; used to insult someone whose speech is crude or unpleasant.
狗嘴里吐不出象牙/ 狗嘴裏吐不出象牙 a filthy mouth cannot utter decent language
literally translated as "no ivory comes from the mouth of a dog"; one cannot expect decent or polite words from a person with a vulgar or malicious characterless mind