The term stems from the classical Latin or its ancient Greek etymon Pharos, meaning lighthouse (Pharos was also the proper name of the famed lighthouse of Alexandria) and the Greek root “logos" (a word or discourse) in John Purdy's The Colombian Navigator; Or, Sailing Directory for the American Coasts and the West-Indies.
[1] It was again used in Purdy's The New Sailing Directory for the Strait of Gibraltar and the Western Division of the Mediterranean Sea: Comprehending the Coasts of Spain, France, and Italy, from Cape Trafalgar to Cape Spartivento, the Balearic Isles, Corsica, Sardinia, Sicily and the Maltese Islands, with the African Coast, from Tangier to Tripoli, Inclusive ...
[2] The term's usage was recognized in The Nautical Magazine: A Journal of Papers on Subjects Connected with Maritime Affairs, Volume 13 as "bestowing a passing notice... which has for some time cut a figure, sublime or ridiculous, in our books of sailing directions".
[3] The term, pharology, first appeared in the Transactions of the Royal Society of Arts of London in 1847 and credited its coinage as "being first introduced by the late Mr [John] Purdy".
[8] More recently, pharology has re-appeared as an obscure or niche area of expertise that focuses on lighthouses and signal lights that surpasses hobby interests.