As said Calixto, " merca " It is cocaine in lunfardo. The story begins in the first half of the 20th century when, in Argentina, coca had a medicinal use, but because of its toxicity distribution was very controlled; The Merck laboratory produced it and was in hospital pharmacies. Despite this, she was often stolen and illegally sold for recreational use. And he was " said to assess their quality of Merck ". Later was like " the merc " and after " the merca " , by associating his name with the apocope of " merchandise ".