All etymologies from the Online Etymology Dictionary
theology [The study of god or gods.]
[the field of study and analysis that treats of God and of God's attributes and relations to the universe; study of divine things or religious truth; divinity.] mid-14c., from O.Fr. theologie "philosophical treatment of Christian doctrine" (14c.), from L. theologia, from Gk. theologia "an account of the gods", from theologos "one discoursing on the gods", from theos "god" (Thea; fem. proper name, from Gk. thea "goddess", fem. equivalent of theos "god", from PIE base *dhes-, root of words applied to various religious concepts, e.g. L. feriae "holidays", festus "festive", fanum "temple".) + -logos "treating of".
sophiology [The study of wisdom.]
coined from Gk. sophi- "wisdom" + -logia "study of". from O.Fr. sophie, from L. sophia, from Gk. sophia, from sophia "skill, wisdom, knowledge", of unknown origin.
religion ["Religionswissenschaft or Religiology?" by R Pummer, 1972. The study of religions, not beliefs.]
c.1200, "state of life bound by monastic vows", also "conduct indicating a belief in a divine power", from Anglo-Fr. religiun (11c.), from O.Fr. religion "religious community", from L. religionem (nom. religio) "respect for what is sacred, reverence for the gods", in L.L. "monastic life" (5c.); according to Cicero, derived from relegare "go through again, read again", from re- "again" + legere "read" (see lecture). However, popular etymology among the later ancients (and many modern writers) connects it with religare "to bind fast" (see rely), via notion of "place an obligation on", or "bond between humans and gods". Another possible origin is religiens "careful", opposite of negligens. Meaning "particular system of faith" is recorded from c.1300. "To hold, therefore, that there is no difference in matters of religion between forms that are unlike each other, and even contrary to each other, most clearly leads in the end to the rejection of all religion in both theory and practice. And this is the same thing as atheism, however it may differ from it in name." [Pope Leo XIII, Immortale Dei, 1885] Modern sense of "recognition of, obedience to, and worship of a higher, unseen power" is from 1530s. Religious is first recorded early 13c. Transfered sense of "scrupulous, exact" is recorded from 1590s.
anthropology [The study of people.]
"science of the natural history of man", 1590s, coined from Gk. anthropo- + -logia "study of". In Aristotle, anthropologos is used literally, as "speaking of man". Related: Anthropological (1825); anthropologist (1798).
hagiology [The study of saints, not the study of what is holy or sacred.]
"study of saints' lives", 1807, from Gk. hagios "holy" + logia "study". First element probably cognate with Gk. agnos "chaste", Skt. yajati "reveres (a god) with sacrifices, worships", O.Pers. ayadana "temple". Hagiographical is attested from 1585.
sacrology [The study of the sacrum bone, not the study of the sacred.]
"bone at the base of the spine", 1753, from L.L. os sacrum "sacred bone", from L. os "bone" + sacrum, neut. of sacer "sacred". Said to be so called because the bone was the part of animals that was offered in sacrifices. Translation of Gk. hieron osteon. But Gk. hieros also can mean "strong." [Sacrology® is a registered trademark used for Teaching In the Field of Achieving Balance In the Sacrum and the Sacroiliac Joint]
eschatology [The study of ends.]
1844, from Gk. eskhatos "last, furthest, remote" (from ex "out of") + -logia "a speaking" (in a certain manner). In theology, the study of the four last things: death, judgment, heaven, hell.
ontology [The study of existing.]
"metaphysical science or study of being", 1721, from Mod.L. ontologia (coined in Fr. by Jean le Clerc, 1692), from Gk. on (gen. ontos) "being" (prp. of einai "to be;" see essence) + -logia "writing about, study of".
philosophy [The love of wisdom.]
c.1300, from O.Fr. filosofie (12c.), from L. philosophia, from Gk. philosophia "love of knowledge, wisdom", from philo- "loving" + sophia "knowledge, wisdom", from sophis "wise, learned". "Nec quicquam aliud est philosophia, si interpretari velis, praeter studium sapientiae; sapientia autem est rerum divinarum et humanarum causarumque quibus eae res continentur scientia." [Cicero, "De Officiis"] Meaning "system a person forms for conduct of life" is attested from 1771. Philosophize is attested from 1594.
neurology [The study of the nervous system, including the brain.]
"scientific study of the nervous system", 1681, from Mod.L. neurologia, from Mod.Gk. neurologia (1664), from neuro- (Gk. neuro-, comb. form of neuron "nerve", originally "sinew, tendon, cord, bowstring", also "strength, vigor", from PIE *sneurom (cf. L. nervus; ate 14c., nerf "sinew, tendon", from M.L. nervus "nerve", from L. nervus "sinew, tendon", metathesis of pre-L. *neuros, from PIE *(s)neu- (cf. Skt. snavan- "band, sinew", Arm. neard "sinew", Gk. neuron "sinew, tendon", in Galen "nerve").) + -logia "study."
phrenology [The study of the mind, through measurement of bumps on the skull.]
1815, from Gk., lit. "mental science", from phren (gen. phrenos) "mind" + -logy "study of". Applied to the theory of mental faculties originated by Gall and Spurzheim that led to the 1840s mania for reading personality clues in the shape of one's skull and the "bumps" of the head. [see Retrophrenology]
psychology [The study of the mind, not the study of the spirit.]
1653, "study of the soul", probably coined mid-16c. in Germany by Melanchthon as Mod.L. psychologia, from Gk. psykhe- "breath, spirit, soul" (1647, "animating spirit", from L. psyche, from Gk. psykhe "the soul, mind, spirit, breath, life, the invisible animating principle or entity which occupies and directs the physical body" (personified as Psykhe, the lover of Eros), akin to psykhein "to blow, cool", from PIE base *bhes- "to blow" (cf. Skt. bhas-). The word had extensive sense development in Platonic philosophy and Jewish-infl. theological writing of St. Paul. In Eng., psychological sense is from 1910.) + logia "study of". Meaning "study of the mind" first recorded 1748, from G. Wolff's Psychologia empirica (1732); main modern behavioral sense is from 1895.
mentology [The study of the mind. Not the study of meaning.]
mean (v.) [meaning]
O.E. mænan "to mean, tell, say, complain", from W.Gmc. *mainijanan (cf. O.Fris. mena, Du. menen, Ger. meinen to think, suppose, be of the opinion"), from PIE *meino- "opinion, intent" (cf. O.C.S. meniti "to think, have an opinion", O.Ir. mian "wish, desire", Welsh mwyn "enjoyment"), probably from base *men- "think."
early 15c., from M.Fr. mental, from L.L. mentalis "of the mind," from L. mens (gen. mentis) "mind", from PIE base *men- "to think" (cf. Skt. matih "thought, mind," Goth. gamunds, O.E. gemynd "memory, remembrance", Mod.Eng. mind). Meaning "crazy, deranged" is from 1927.
etymology [The study of historical linguistic change, esp. as manifested in individual words. Not the study of truth.]
late 14c., from Gk. etymologia, from etymon "true sense" (neut. of etymos "true," related to eteos "true") + logos "word." In classical times, of meanings; later, of histories. Latinized by Cicero as veriloquium.
semantics [The study of meaning in symbols, not the meaning of life.]
"science of meaning in language", 1893, from Fr. sémantique (1883); see semantic (1894, from Fr. sémantique, applied by Michel Bréal (1883) to the psychology of language, from Gk. semantikos "significant", from semainein "to show, signify, indicate by a sign", from sema "sign" (Doric sama).) (also see -ics). Replaced semasiology (1847), from Ger. Semasiologie (1829), from Gk. semasia "signification, meaning."
[also called semiology] study of signs and symbols with special regard to function and origin, 1880, from Gk. semeiotikos "observant of signs", adj. form of semeiosis "indication", from semeioun "to signal", from sema "sign".