Wiktionary
mastika
n. 1 A type of hard resin found on various acacia trees, which can be chewed. 2 A liquor made from such resin. 3 A liqueur similar to raki made from anise or other sources, made in the Balkans. 4 A serving of such a beverage.
Wikipedia
Mastika
Mastika is a liqueur seasoned with mastic, a resin gathered from the mastic tree, a small evergreen tree native to the Mediterranean region. A variant is Mastiha, which is produced on the Greek island of Chios and has a protected designation of origin in the European Union.
The name of the resin, whence the name of the drink, is derived from the Greek "to chew, to gnash the teeth".