Etymology
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librarian (n.)
"custodian of a library," 1713; see library + -an. Earlier form was library-keeper (1640s), and librarian had been used in the sense "scribe, one who copies books" (1660s).
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anencephalic (adj.)

"having no brain" (biology), 1821, with -ic + Latinized form of Greek anenkephalos, from an- "not, without" (see an- (1)) + enkephalos "brain," "the brain," literally "within the head," from en "in" (see en- (2)) + kephalē "head;" see cephalo-. Related: Anencephalous (1834); anencephalia; anencephaly.

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anorexia (n.)
1590s, "morbid want of appetite," Modern Latin, from Greek anorexia, from an- "without" (see an- (1)) + orexis "appetite, desire," from oregein "to desire, long for," literally "reach out (one's hand), stretch oneself, stretch out for" (from PIE root *reg- "move in a straight line") + abstract noun ending -ia. In current use, often short for anorexia nervosa.
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Puerto Rican 

1873 (n.), "native or inhabitant of Puerto Rico;" 1874 (adj.), "of or pertaining to Puerto Rico or its inhabitants and culture," from Puerto Rico + -an. Earlier was Porto Rican (1842).

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anesthesia (n.)

1721, "loss of feeling," medical Latin, from Greek anaisthēsia "want of feeling or perception, lack of sensation (to pleasure or pain)," abstract noun from an- "without" (see an- (1)) + aisthēsis "feeling," from PIE root *au- "to perceive." For the abstract noun ending, see -ia. As "a procedure for the prevention of pain in surgical operations," from 1846. Aesthesia "capacity for feeling" is attested in English from 1853, perhaps a back-formation.

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authoritarian (adj.)
"favoring imposed order over freedom," 1862, from authority + -an. Compare authoritative, which originally had this meaning to itself. Noun in the sense of one advocating or practicing the principle of authority over individual freedom is from 1859.
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subterranean (adj.)
c. 1600, from Latin subterraneus "underground," from sub "under, beneath" (see sub-) + terra "earth, the ground" (from PIE root *ters- "to dry") + -an.
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chthonian (adj.)

"subterranean," 1804, with -an + Latinized form of Greek khthonios "of the earth, in the earth," from khthōn "the earth, solid surface of the earth" (mostly poetic), from PIE root *dhghem- "earth."

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ostracean (adj.)

"resembling an oyster," 1840, with -an + Latinized form of Greek ostrakios, from ostreion "oyster," from PIE *ost-r-, from root *ost- "bone." Related ostraceous (by 1834).

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Pythian (adj.)

c. 1600, "pertaining to Delphi or Delphic Apollo," from Pythia + -an. As a noun from 1590s. The Pythian Games were one of the four great national festivals of ancient Greece, held every four years at Delphi in honor of Apollo.

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