The Warlpiri people, a group of Indigenous Australian, teach a strange language called Tjiliwirri to their boys who go through an initiation rite. Tjiliwirri literally means “funny’ or “clown”. The peculiar thing about this language is that it expresses every idea as its opposite. For instance, if you want to say “It’s hot”, you have to say “It’s cold”. It can quickly get complicated. Saying “I bought an apple” would mean “You sold an apple”.
SpongeBob would have been thrilled to know that the boys of Warlpiri celebrate “Opposite Day” every day:
Reference (Click to Show)
Harold Koch & Rachel Nordlinger (2014). The Languages and Linguistics of Australia: A Comprehensive Guide