Douglas Harper's Etymology Dictionary
1914, "excessive fear of snakes or reptiles," from ophidio- apparently extracted from Modern Latin ophidia, a word coined arbitrarily (to provide an -ia form to serve as an order name in taxonomy) from Greek ophis "serpent" (see ophio-) + -phobia.
Wiktionary
n. ophiophobia.
Wikipedia
Ophidiophobia or ophiophobia is a particular type of specific phobia, the abnormal fear of snakes. Fear of snakes is sometimes called by a more general term, herpetophobia, fear of reptiles and/or amphibians. The word comes from the Greek words "ophis" which refers to snake and "phobia" meaning fear.
Care must also be taken to differentiate people who do not like snakes or fear them for their venom or the inherent danger involved. An ophidiophobe would not only fear them when in live contact but also dreads to think about them or even see them on TV or in pictures.
About a third of adult humans are ophidiophobic, making this the most common reported phobia. Scientists have theorised that humans may have an innate reaction to snakes, which was vital for the survival of humankind as it allowed such dangerous threats to be identified immediately.