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"irrational fear, horror, aversion," 1786, perhaps on model of similar use in French, abstracted from compounds in -phobia, from Greek -phobia, from phobos "fear, panic fear, terror, outward show of fear; object of fear or terror," originally "flight" (still the only sense in Homer), but it became the common word for "fear" via the notion of "panic, fright" (cf. phobein "put to flight, frighten"), from PIE root *bhegw- "to run" (cf. Lithuanian begu "to flee;" Old Church Slavonic begu "flight," bezati "to flee, run;" Old Norse bekkr "a stream"). Psychological sense attested by 1895.
word-forming element meaning "excessive or irrational fear of," from Latin -phobia and directly from Greek -phobia "panic fear of," from phobos "fear" (see phobia). In widespread popular use with native words from c.1800. Related: -phobic.
phobia pho·bi·a (fō'bē-ə)
A persistent, abnormal, or irrational fear of a specific thing or situation that compels one to avoid the feared stimulus.
A strong fear, dislike, or aversion.
An intense, abnormal, or illogical fear of a specified thing: claustrophobia.
An extreme and often unreasonable fear of some object, concept, situation, or person.