Clenching the teeth is generally displayed by humans and other animals as a display of anger, hostility or frustration. It is thought that in humans, clenching the teeth may be an evolutionary instinct to display teeth as weapons, thereby threatening a rival or a predator. The phrase "to grit one's teeth" is the grinding or clenching of the teeth in anger, or to accept a difficult or unpleasant situation and deal with it in a determined way. In the Bible there are several references to "gnashing of teeth" in both the Old Testament, and the New Testament, where the phrase "wailing and gnashing of teeth" describes what an imaginary king believes is occurring in the darkness outside of his son's wedding venue.() In David Lynch's 1977 film "Eraserhead", Henry Spencer's partner ("Mary X") is shown tossing and turning in her sleep, and snapping her jaws together violently and noisily, depicting sleep bruxism. In Stephen King's 1988 novel "The Tommyknockers", the sister of central character Bobbi Anderson also had bruxism. In the 2000 film "Requiem for a Dream", the character of Sara Goldfarb (Ellen Burstyn) begins taking an amphetamine-based diet pill and develops bruxism. In the 2005 film "Beowulf & Grendel", a modern reworking of the Anglo-Saxon poem "Beowulf", Selma the witch tells Beowulf that the troll's name Grendel means "grinder of teeth", stating that "he has bad dreams", a possible allusion to Grendel traumatically witnessing the death of his father as a child, at the hands of King Hrothgar. The Geats (the warriors who hunt the troll) alternatively translate the name as "grinder of men's bones" to demonize their prey. In George R. R. Martin's "A Song of Ice and Fire" series, King Stannis Baratheon grinds his teeth regularly, so loudly it can be heard "half a castle away". In rave culture, recreational use of ecstasy is often reported to cause bruxism. Among people who have taken ecstasy, while dancing it is common to use pacifiers, lollipops or chewing gum in an attempt to reduce the damage to the teeth and to prevent jaw pain. Bruxism is thought to be one of the contributing factors in "meth mouth", a condition potentially associated with long term methamphetamine use.