Etymology
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newborn (adj.)

also new-born, "just born or very lately born," c. 1300, from new + born. As a noun, "a newborn child," from 1879.

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baby (n.)

late 14c., babi, "infant of either sex," diminutive of babe (q.v.) with -y (3).

The meaning "childish adult person" is from c. 1600. The sense of "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 was boosted by baby vamp "a popular girl" (see vamp (n.2)), student slang from c. 1922.

The 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, perhaps for the reduplication as well as the fact that more infants have blue eyes than keep the color (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.)

"temporary marked increase in the birth rate," coined 1941 from baby (n.) + boom (n.2); derivative baby-boomer (member of the one that began in the U.S. in 1945) is recorded by 1963 (in newspaper articles when they began to approach college age); earlier it had sometimes meant "a young kangaroo."

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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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neonatal (adj.)

also neo-natal, "relating to newborn children," 1883, from neo- + natal.

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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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neonatology (n.)

branch of medicine concerned with newborn infants, 1960, from neonate "recently born infant" + -ology.

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vagitus (n.)

crying of a newborn child, 1650s, from Latin vagitus "a crying, squalling," from vagire (see sough (v.)).

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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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