Such fears are psychological rather than physiological in origin, and few of these terms are found in medical literature. In ancient Greek mythology Phobos was the twin brother of Deimos (terror). The word phobia may also refer to conditions other than true phobias. For example, the term hydrophobia is an old name for rabies, since an aversion to water is one of that diseases symptoms. A specific phobia to water is called aquaphobia instead. A hydrophobe is a chemical compound that repels water. Similarly, photophobia usually refers to a physical complaint (aversion to light due to inflamed eyes or excessively dilated pupils), rather than an irrational fear of light. Non-medical, deterrent and political use
Several terms with the suffix -phobia are used non-clinically to imply irrational fear or hatred. Examples include:

Chemophobia – Irrational fear or hatred of chemistry and synthetic chemicals. Xenophobia – Irrational fear or hatred of strangers or the unknown, sometimes used to describe nationalistic political beliefs and movements. Homophobia – Irrational fear or hatred of homosexuality or people who identify or perceived as being lesbian, gay, bisexual or transgender (LGBT). Islamophobia – Irrational fear or hatred of Islam
Hinduphobia – Irrational fear or hatred of Hinduism or Sanatan Dharma
Biphobia – Irrational fear or hatred of bisexual people
Transphobia – Irrational fear or hatred of transgender peopleUsually, these kinds of "phobias" are described as fear, dislike, disapproval, prejudice, hatred, discrimination, or hostility towards the object of the "phobia". It is a form of hyperbole.
Mechanism
Limbic system
Beneath the lateral fissure in the cerebral cortex, the insula, or insular cortex, of the brain has been identified as part of the limbic system, along with the cingulated gyrus, hippocampus, corpus callosum, and other nearby cortices. This system has been found to play a role in emotion processing, and the insula, in particular, may contribute to maintaining autonomic functions. Studies by Critchley et al. indicate the insula as being involved in the experience of emotion by detecting and interpreting threatening stimuli. Similar studies monitoring insula activity have shown a correlation between increased insular activation and anxiety.In the frontal lobes, other cortices involved with phobia and fear are the anterior cingulate cortex and the medial prefrontal cortex. In the processing of emotional stimuli, studies on phobic reactions to facial expressions have indicated that these areas are involved in the processing and responding to negative stimuli. The ventromedial prefrontal cortex has been said to influence the amygdala by monitoring its reaction to emotional stimuli or even fearful memories. Most specifically, the medial prefrontal cortex is active during the extinction of fear and is responsible for long-term extinction. Stimulation of this area decreases conditioned fear responses, so its role may be in inhibiting the amygdala and its reaction to fearful stimuli.The hippocampus is a horseshoe-shaped structure that plays an essential part in the brains limbic system. This is because it forms memories and connects them with emotions and the senses.