The expression to be a bore had been used in print in the sense of "to be tiresome or dull" since 1768 at the latest.[4] The expression "boredom" means "state of being bored," 1852, from bore (v.1) + -dom. It also has been employed in a sense "bores as a class" (1883) and "practice of being a bore" (1864, a sense properly belonging to boreism, 1833).[5] The word "bore" as a noun meaning a "thing which causes ennui or annoyance" is attested to since 1778; "of persons by 1812". The noun "bore" comes from the verb "bore", which had the meaning "[to] be tiresome or dull" first attested [in] 1768, a vogue word c. 1780–81 according to Grose (1785); possibly a figurative extension of "to move forward slowly and persistently, as a [hole-] boring tool does."[6]

“Time is quixotic because it can torment us. When we have insufficient stimulus to fill our lives, we resent the relentless quality of time, and we engage in activities designed to “kill time.” Time that passes slowly creates insufferable boredom; time that passes to quickly makes us aware of our accelerated death march. A person’s perspective on time depends mostly on what they are most afraid of, boredom or death.”
^ Vodanovich, Stephen J. (November 2003) "Psychometric Measures of Boredom: A Review of the Literature" The Journal of Psychology. 137:6 p. 569 "Indeed, a shortcoming of the boredom literature is the absence of a coherent, universally accepted definition. The lack of an agreed-upon definition of boredom has limited the measurement of the construct and partly accounts for the existence of diverse approaches to assessing various subsets of boredom."

Boredom is similar to mental fatigue and is caused by repetition and lack of interest in the details of our tasks (such as tasks that require continuous attention, waiting at the airport, prisoners locked in cells). Any experience that is predictable and repetitive becomes boring. In general, too much of the same thing and too little stimulation can cause in its victim an absence of desire and a feeling of entrapment (Toohey, 2012).    

A 1989 study indicated that an individual's impression of boredom may be influenced by the individual's degree of attention, as a higher acoustic level of distraction from the environment correlated with higher reportings of boredom.[32] Boredom has been studied as being related to drug abuse among teens.[33] Boredom has been proposed as a cause of pathological gambling behavior. A study found results consistent with the hypothesis that pathological gamblers seek stimulation to avoid states of boredom and depression.[34] It has been suggested that boredom has an evolutionary basis that encourages humans to seek out new challenges. It may influence human learning and ingenuity.[35]

Lethargy is a state of tiredness, weariness, fatigue, or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to boredom, inadequate sleep, overexertion, overworking, stress, lack of exercise, or a symptom of a disorder. When part of a normal response, lethargy often resolves with rest, adequate sleep, decreased stress, and good nutrition.[21][22]
Boredom also has its benefits. It is important to see boredom as a “call to action” (Svendsen, 1999). Nietzsche suggested that men of rare sensibility value boredom as an impetus to achievement. Boredom can be a catalyst for action. It can provide an opportunity for thought and reflection. It can also be a sign that a task is a waste of time—and thus not worth continuing.
Absent-mindedness is where a person shows inattentive or forgetful behaviour.[20] Absent-mindedness is a mental condition in which the subject experiences low levels of attention and frequent distraction. Absent-mindedness is not a diagnosed condition but rather a symptom of boredom and sleepiness which people experience in their daily lives. When suffering from absent-mindedness, people tend to show signs of memory lapse and weak recollection of recently occurring events. This can usually be a result of a variety of other conditions often diagnosed by clinicians such as attention deficit hyperactivity disorder and depression. In addition to absent-mindedness leading to an array of consequences affecting daily life, it can have as more severe, long-term problems.
"Meh" is an interjection used as an expression of indifference or boredom. It may also mean "be it as it may".[40] It is often regarded as a verbal shrug of the shoulders. The use of the term "meh" shows that the speaker is apathetic, uninterested, or indifferent to the question or subject at hand. It is occasionally used as an adjective, meaning something is mediocre or unremarkable.[41]
“Alcohol makes other people less tedious, and food less bland, and can help provide what the Greeks called entheos, or the slight buzz of inspiration when reading or writing. The only worthwhile miracle in the New Testament—the transmutation of water into wine during the wedding at Cana—is a tribute to the persistence of Hellenism in an otherwise austere Judaea. The same applies to the seder at Passover, which is obviously modeled on the Platonic symposium: questions are asked (especially of the young) while wine is circulated. No better form of sodality has ever been devised: at Oxford one was positively expected to take wine during tutorials. The tongue must be untied. It's not a coincidence that Omar Khayyam, rebuking and ridiculing the stone-faced Iranian mullahs of his time, pointed to the value of the grape as a mockery of their joyless and sterile regime. Visiting today's Iran, I was delighted to find that citizens made a point of defying the clerical ban on booze, keeping it in their homes for visitors even if they didn't particularly take to it themselves, and bootlegging it with great brio and ingenuity. These small revolutions affirm the human.”
Erich Fromm and other thinkers of critical theory speak of boredom as a common psychological response to industrial society, where people are required to engage in alienated labor. According to Fromm, boredom is "perhaps the most important source of aggression and destructiveness today." For Fromm, the search for thrills and novelty that characterizes consumer culture are not solutions to boredom, but mere distractions from boredom which, he argues, continues unconsciously.[29] Above and beyond taste and character, the universal case of boredom consists in any instance of waiting, as Heidegger noted, such as in line, for someone else to arrive or finish a task, or while one is travelling somewhere. The automobile requires fast reflexes, making its operator busy and hence, perhaps for other reasons as well, making the ride more tedious despite being over sooner.
People who lack self-awareness are more prone to boredom. A bored individual is unable to articulate what it is that he or she desires or wants to do. They have trouble describing their feelings. An inability to know what will make one happy can lead to a more profound existential boredom. Not knowing what we are searching for means that we lack the capacity to choose appropriate goals for engagement with the world (Eastwood, 2012).