Well, the word has an interesting background. It comes from MELAS(=black) and CHOLI(= bile) and it refers to someone deep in black bile, therefore glum, sad. The idea that the human feelings are related to a good balance of body fluids was very widespread in the antiquity.
Hippocrates taught that these fluids are: blood, bile, black bile and phlegm. Consequently, if the black bile prevails, you get the feeling of discontent, sorrow, ….something like the way we are feeling now!
Warm greetings to all of you.
*As always, info from G. Babiniotis’: “Etymology Dictionary of Modern Greek”