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.
1866 in archaeology, "belonging to the middle Stone Age (in Europe, roughly 15,000 to 5,000 years before the present, between the paleolithic and the neolithic); see meso- "middle" + lithic "consisting of stone." The word was used c. 1859 in a different sense in geology.
1921; see jazz (n.); popularized 1922 in writings of F. Scott Fitzgerald; usually regarded as the years between the end of World War I (1918) and the Stock Market crash of 1929.
We are living in a jazz age of super-accentuated rhythm in all things; in a rhythm that (to "jazz" a word) is super-normal, a rhythm which is the back-flare from the rhythm of a super war. ["Jacobs' Band Monthly," Jan. 1921]