Etymology
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baby (n.)

late 14c., babi, "infant of either sex," diminutive of babe (see babe) with -y (3). Meaning "childish adult person" is from c. 1600. Meaning "youngest of a group" is by 1897. As a term of endearment for one's lover it is attested perhaps as early as 1839, certainly by 1901 (OED writes, "the degree of slanginess in the nineteenth-century examples is not easily determinable"); its popularity perhaps boosted by baby vamp "a popular girl" (see vamp (n.2)), student slang from c. 1922.

Meaning "minute reflection of oneself seen in another's eyes" is from 1590s (compare pupil (n.2)). As an adjective by 1750. Baby food is from 1833. Baby blues for "blue eyes" recorded by 1892 (the phrase also was used for "postpartum depression" 1950s-60s). To empty the baby out with the bath (water) is attested by 1909 (in G.B. Shaw; compare German das Kind mit dem Bade ausschütten, attested from 17c.). A baby's breath was noted for sweet smell, which also was supposed to attract cats, hence baby's breath as the name of a type of flower, attested from 1897. French bébé (19c.) is said to be from English, but there were similar words in the same sense in French dialects.

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baby (v.)
"to treat like a baby," 1742, from baby (n.). Related: Babied; babying.
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baby boom (n.)
coined 1941, from baby (n.) + boom (n.); derivative baby-boomer (member of the one that began in the U.S. in 1945) is recorded by 1974.
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baby-farmer (n.)
"one who cares for the infants of those unable or unwilling to do so themselves," 1868, from baby (n.) + farmer. Related: Baby-farm.
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babysit (v.)
also baby-sit, 1947, from baby (n.) + sit (v.); figurative use (often contemptuous) by 1968. Babysitting is from 1946.
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babyish (adj.)
"like a baby, extremely childish," 1753, from baby (n.) + -ish. Earlier in same sense was babish (1530s). Related: Babyishness.
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moppet (n.)

endearing term for a baby, a girl, etc., c. 1600," also "puppet made of cloth, rag-baby" (Johnson, 1755), from Middle English moppe "little child, baby doll" (mid-15c.) + -et, diminutive suffix. The Middle English word also meant "simpleton, fool," and may have been cognate with Low German mop "simpleton" [Barnhart]. Or, if "baby doll" is the original sense in Middle English, perhaps it is from Latin mappa "napkin, tablecloth," hence "rag doll."

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crybaby (n.)

also cry-baby, derisive word for one who cries too easily or too much, 1851, American English, from cry + baby (n.).

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babysitter (n.)

also baby-sitter, "person who looks after a child or children while the parents are away," 1914, from baby (n.) + agent noun from sit (v.). Short form sitter is attested from 1937.

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yummy 
"delicious," 1899, from baby talk. Yum-yum as an exclamation of pleasure is recorded from 1878.
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