Why did van goh cut off his left ear?

You're thinking of absinthe, sometimes known as the Green Fairy because of its brilliant green color. It's made primarily of wormwood, anise, and fennel, but contains other herbs as well. It is bottled without added sugar, so it is not a liqueur in the strictest sense. It is traditionally served in a special glass, which has a bulb at the bottom to indicate the proper amount. A special slotted spoon is set over the top of the glass and a sugar cube is set on the spoon. Cold water is then poured slowly into the glass over the sugar cube until it dissolves and the drink is diluted 3:1 or 5:1. This is called louching the absinthe. During this process, some of the plant compounds come out of solution, releasing flavor into the drink and thickening its mouth feel. Because of the supposed hallucinogenic properties of absinthe, which are due to the chemical thujone in wormwood, it is heavily regulated in many parts of the world. Regulations vary from country to country, and often are focused on importation rather than possession or consumption.