Etymology
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Iron Age 
1590s, originally, as in Greek and Roman mythology, the last and worst age of the world; the archaeological sense of "period in which humans used iron tools and weapons" is from 1866 (earlier in this sense iron period, 1847).
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age (n.)

late 13c., "long but indefinite period in human history," from Old French aage, eage (12c., Modern French âge) "age; life, lifetime, lifespan; maturity," earlier edage (11c.), from Vulgar Latin *aetaticum (source also of Spanish edad, Italian eta, Portuguese idade "age"), extended form of Latin aetatem (nominative aetas), "period of life, age, lifetime, years," from aevum "lifetime, eternity, age," from PIE root *aiw- "vital force, life; long life, eternity"

Expelled native eld (Old English eald) "old age; an age; age as a period of life." Meaning "time something has lived, particular length or stage of life" is from early 14c. Used especially for "old age" since early 14c.; meaning "effects of old age" (feebleness, senility, etc.) is from mid-15c. In geology, in reference to great periods in the history of the earth, 1855; in archaeology, from 1865 (Stone Age, etc.) naming periods for the materials employed for weapons and tools. Sometimes in early modern English "a century" (similar to French siècle "century," literally "an age"), hence plural use in Dark Ages, Middle Ages. To act (one's) age "behave with appropriate maturity" is attested by 1927.

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age (v.)
late 14c., "grow old," from age (n.). Transitive meaning "make old" is early 15c.
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iron (n.)

Middle English iron, iren, yron, from Old English iren, variant (with rhotacism of -s-) of isen, later form of isern, isærn "the metal iron; an iron weapon or instrument," from Proto-Germanic *isarn (source also of Old Saxon isarn, Old Frisian isern, Old Norse isarn, Middle Dutch iser, Old High German isarn, German Eisen).

This perhaps is an early borrowing of Celtic *isarnon (compare Old Irish iarn, Welsh haiarn), which Watkins suggests is from PIE *is-(e)ro- "powerful, holy," from PIE *eis "strong" (source also of Sanskrit isirah "vigorous, strong," Greek ieros "strong"), on the notion of "holy metal" or "strong metal" (in contrast to softer bronze).

It was both an adjective and a noun in Old English, but in form it is an adjective. The alternative isen survived into early Middle English as izen. In southern England the Middle English word tended to be ire, yre, with loss of -n, perhaps regarded as an inflection; in the north and Scotland, however, the word tended to be contracted to irn, yrn, still detectable in dialect.

Right so as whil that Iren is hoot men sholden smyte. [Chaucer, c. 1386]

Chemical symbol Fe is from the Latin word for the metal, ferrum (see ferro-). Meaning "metal device used to press or smooth clothes" is from 1610s. Meaning "golf club with an iron head, 1842. To have (too) many irons in the fire "to be doing too much at once" is from 1540s. Iron lung "artificial respiration tank" is from 1932. The iron crown was that of the ancient kings of Lombardy, with a thin band of iron in the gold, said to have been forged from a nail of Christ's Cross. Iron horse "railroad locomotive" is from an 1839 poem. Iron maiden, instrument of torture, is from 1837 (probably translating German eiserne jungfrau). The unidentified French political prisoner known as the man in the iron mask died in the Bastille in 1703. In British history, Wellington was called the Iron Duke by 1832.

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-age 
word-forming element in nouns of act, process, function, condition, from Old French and French -age, from Late Latin -aticum "belonging to, related to," originally neuter adjectival suffix, from PIE *-at- (source of Latin -atus, past participle suffix of verbs of the first conjugation) + *-(i)ko-, secondary suffix forming adjectives (see -ic).
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iron (v.)
c. 1400, irenen, "to make of iron," from iron (n.). Meaning "shackle with irons" is from 1650s. Meaning "press clothes" (with a heated flat-iron) is recorded from 1670s. Related: Ironed; ironing.
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Iron Cross 
from German eiserne kreuz, instituted 1813 by Frederick Wilhelm III of Prussia, originally for distinguished military service in the wars against Napoleon.
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New Age (adj.)
1971, in reference to a modern spiritual movement, from new + age (n.). It had been used at various times at least since the 1840s.
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ice age (n.)
1855, from ice (n.) + age (n.). Perhaps translating German Eiszeit (1837). An earlier term in the same sense was glacial epoch (1841). Local scientific men had noticed from the late 18c. evidence that the Alpine glaciers once had been much larger; in the 1830s stray boulders, moraines, and polished bedrock in northern Europe (formerly interpreted as relics of catastrophic floods) began to be understood as revealing the former presence of a large ice cap there. When Agassiz, a convert to the theory, came to America in 1846 he found similar evidence in New England. The glacial theory and the notion that there had been several worldwide ice ages seems to have been generally accepted by the 1870s.
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age-group (n.)
1876, originally a term in the science of demographics, from age (n.) + group (n.).
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