It's the direct translation of the French term "eau de toilette"

The scented things we put on ourselves to cover up our icky human scent fall into a couple of different categories based upon how much scent is actually in it.

Perfume, also called extract or extrait perfume, can include 15-40% perfume concentrates. This is the purest form of scented product and is the most expensive as a result.

Eau de parfum contains about 7-15% perfume concentrates. This is the most popular and common form of perfume. It provides a long-lasting fragrance and generally doesn't cost as much as extract perfume.

Eau de toilette has around 1-6% perfume concentrates. This makes for a light scent that doesn't linger as long as the more intense versions. It was originally intended to be a refreshing body splash to help people wake up in the morning.

Eau de cologne is sometimes used interchangeably with the term eau de toilette. However, the concoction began as the name of a light, fresh fragrance mixed with citrus oils and was made popular by Napoleon. Some perfumers today have a version of this called eau fraiche.