`Monday morning blues’

Monday is not a day that many people look forward to. In fact, most people get up feeling rather depressed on this day. Reason? They know they have to work for another five or six days before they get some time off. The `blues’ referred to in the idiom has nothing to do with the colour. According to some scholars, it refers to the type of music made popular by African Americans. The `blues music’ deals with rather sad themes, and as a result leaves the listener feeling sad. This is the reason why the expressions `to have the blues’ and `feeling blue’ mean feeling sad or depressed.

Source: ‘Know Your English’ ( The Hindu) – May 15, 2006