The pronunciation of this word sums up its very definition, that of someone who is covetous, a green-eyed monster if you will.
In Othello, Shakespeare also alludes to cats as green-eyed monsters in the way that they play with mice before killing them.
O, beware, my lord, of jealousy;
It is the green-eyed monster which doth mock
The meat it feeds on; that cuckold lives in bliss
Who, certain of his fate, loves not his wronger;
But, O, what damned minutes tells he o'er
Who dotes, yet doubts, suspects, yet strongly loves!