A "Writ of Garnishment" is the legal means by which a creditor forces someone who owes a debtor something to pay it to the creditor instead. Usually, a writ of garnishment is directed to a bank or employer and designed to secure a debtor's bank account or wages.
Some people say that one can "garnish" the wages. Others prefer to say that one can "garnishee" the wages (a verb usage). The word "garnishee" is also used to refer to the person, usually a bank or employer, upon whom a writ of garnishment is served by the creditor (a noun usage).
The noun usage of the word "garnishee" is widely accepted and is used in Colorado's state judicial system sanctioned forms. The verb usage of the word "garnishee" is a decidedly minority usage (disfavored by a margin of 675-11 in one computerized legal research search, with one citation implying that "garnishee" is incorrect), that should be avoided.
Noted law professor and blogger Eugene Volokh has some good insights on teaching usage and pronunciation generally in an recent essay on the subject, which closely tracks my own views on good grammar pedagogy.