piscatology (n.)

Proto-Indo-European root meaning "a fish."

It forms all or part of: fish; fishnet; grampus; piscatory; Pisces; piscine; porpoise.

It is the hypothetical source of/evidence for its existence is provided by: Latin piscis (source of Italian pesce, French poisson, Spanish pez, Welsh pysgodyn, Breton pesk); Old Irish iasc; Old English fisc, Old Norse fiskr, Gothic fisks.

word-forming element indicating "branch of knowledge, science," now the usual form of -logy. Originally used c. 1800 in nonce formations (commonsensology, etc.), it gained legitimacy by influence of the proper formation in geology, mythology, etc., where the -o- is a stem vowel in the previous element.

The second element is prop[erly] -logy (-logue, etc.), the -o- belonging to the preceding element; but the accent makes the apparent element in E[nglish] to be -ology, which is hence often used as an independent word. [Century Dictionary]