The term I bid you adieu is a colloquial expression that stems from the French language, and is equivalent to the English expressions “goodbye” or “farewell”.
Other than saying goodbye, the term can also be used to express that we plan to stop doing something, like quitting a bad habit. In that case, one can say they bid adieu to that certain thing.
I bid you adieu can be traced back to the 14th century. Originally, it comes from the French expression “à dieu vous comant”, which means “I commend you to God” in English.
The term is widely spread among English-speaking countries as it can be used in various situations.
Nowadays it is considered to be a formal, fancy way of saying goodbye, although it can also be used in a humorous way as well.
I bid you adieu also made appearances in several pop-culture products, like in the animated TV series The Simpsons, where the expression is uttered during the 10th episode of season 13.