There are various meanings ascribed to the monkeys and the proverb including associations with being of good mind, speech and action. In the Western world the phrase is often used to refer to those who deal with impropriety by looking the other way, refusing to acknowledge it, or feigning ignorance.
In Chinese, a similar phrase exists in the Analects of Confucius from 2nd to 4th century B.C.: "Look not at what is contrary to propriety; listen not to what is contrary to propriety; speak not what is contrary to propriety; make no movement which is contrary to propriety" . It may be that this phrase was shortened and simplified after it was brought into Japan.
The monkey is believed to be the messenger of the Hie Shinto shrines, which also have connections with Tendai Buddhism. There are even important festivals that are celebrated during the year of the monkey (occurring every twelve years) and a special festival is celebrated every sixteenth year of the Kōshin.