The French word ennui describes a feeling that combines tiredness and boredom. Ennui is one version of "the blahs."
Though it sounds it little fancy — maybe because it comes from French — ennui is a common feeling that everybody experiences: being bored and tired. School and work fill lots of people with ennui. A terrible TV show could create ennui. If you feel like your life is going nowhere, ennui could set in. When you're feeling ennui, you might as well take a nap, because you're too drowsy and uninterested to do much of anything else.