The origin of the terms "vase", "Amsterdammetje" and "Fluitje" is deeply rooted in Dutch beer culture and has to do with the traditions of drinking beer in different regions of the Netherlands. Although the exact origin cannot always be traced, there are some assumptions about how these terms originated:

1. Vase: The vase owes its name to the characteristic glass in which it is served. Vase -shaped glasses were used in the early 1900s in Dutch cafés and bars. The term "vase" is probably derived from the shape of this glass, that looks like a small vase. The use of this term soon became popular and has now become a common name for a small glass of beer.
2. Amsterdammet: The origin of the Amsterdammet is less clear, but it is often associated with the city of Amsterdam. This term is supposed to have been created in Amsterdam cafés and bars, where it was customary to serve smaller glasses of beer. Adding the suffix "-tje" is typical of the Dutch language and is often used to indicate the shrinking form. That is why a "Amsterdammet" could simply mean a small glass of beer from Amsterdam.
3. Whistle: The term "whistle" may be derived from the sound that is produced when the glass is touched, similar to the sound of a whistle. It could also refer to the long, slender shape of the glass, that looks like a piece of cake. This term has long been used in the Netherlands and has become a common name for a small, high glass of beer.