When was the word phobia coined? And how did the concept of naming different phobias come into existence?
The first quotation in the OED of phobia in English is from 1786. The suffix -phobia is from post-classical Latin -phobia, from Hellenistic Greek -ϕοβία, from ϕόβος (phobe) + ia suffix:
First recorded in the Latin loan hydrophobia n.: this is probably the model for subsequent English formations. Formations within English are found from the 17th cent. (in an isolated example); a handful date from the 18th cent.; from the 19th cent. they are very abundant. Combined with a wide variety of first elements: these may be ultimately of Greek or Latin or English origin. Some pairs of synonyms occur with respectively Latin and Greek first elements, as aquaphobia n., feminophobia n., gynophobia n. at gyno- comb. form , and hydrophobia n. Several formations derive from the names of peoples, as Anglophobia n., Gallophobia n. at Gallo- comb. form1 2b, Germanophobia n., Russophobia n. Occas. modern formations retaining the two elements separately, as school phobia n. at school n.1 Compounds 5a, should perhaps be regarded as compounds with phobia n. as the second element.