The Commentary of Father Monserrate 3.1.8

3.1.8

Indigo and opium are largely grown in the south, and bring no small profit to the royal revenues. Indigo is a plant from which a juice is extracted yielding a blue dye when it hardens. The vernacular name means (as in Persian also) 'blue,' but the Portuguese have added a letter, calling the plant 'anilum' instead of 'nilum.'