1877, from German, literally "eternity," from ewig "everlasting" (from PIE root *aiw- "vital force, life; long life, eternity") + -keit word-forming element meaning "state or condition of being" (see -hood).

"pertaining to or suggestive of the Middle Ages," 1825 (mediaeval), coined in English from Latin medium "the middle" (from PIE root *medhyo- "middle") + aevum "age" (from PIE root *aiw- "vital force, life; long life, eternity").

"pertaining to traditional Hindu science of medicine," 1917, from Sanskrit Ayurveda "science of life," from ayur "life" (from PIE *oyus-, suffixed form of *oyu- "life everlasting," from variant form of root *aiw- "vital force, life; long life, eternity") + veda "knowledge" (see Veda).

1610s, from Late Latin longaevitatem (nominative longaevitas) "great age, long life," from Latin longaevus "of great age, ancient, aged," from longus "long" (see long (adj.)) + aevum "lifetime, age" (from PIE root *aiw- "vital force, life; long life, eternity").

"always, ever," c. 1200, from Old Norse ei "ever" (cognate with Old English a "always, ever"), from Proto-Germanic *aiwi-, extended form of PIE root *aiw- "vital force, life; long life, eternity" (source also of Greek aiōn "age, eternity," Latin aevum "space of time").

"having the same age, having lived for an equal period," 1620s, from Late Latin coaevus"of the same age," from assimilated form of Latin com "with, together" (see com-) + aevum "an age" (from PIE root *aiw- "vital force, life; long life, eternity"). As a noun from c. 1600.

also primaeval, "of or belonging to the first age," 1650s, with -al (1) + Latin primaevus "early in life, youthful," from primus "first" (see prime (adj.)) + aevum "an age" (from PIE root *aiw- "vital force, life; long life, eternity"). Related: Primevally.

"pertaining to life," 1847, also biotical (1847), from Latin bioticus, from Greek biotikos "pertaining to life," from bios "life," from PIE root *gwei- "to live." Biotic factor was in use by 1907. Related: Biotical. Biotics "science of vital functions and manifestations; powers and qualities peculiar to living organisms" (T. Sterry Hunt) is from 1882.

word of negation or refusal, "no" as a reply to a question, late 12c., from a Scandinavian source such as Old Norse nei, compound of ne "not" (from PIE root *ne- "not") + ei "ever," from Proto-Germanic *aiwi-, extended form of PIE root *aiw- "vital force, life; long life, eternity."

"having the same age as another, beginning to exist at the same time," c. 1600, from Late Latin coaetanus "one of the same age," from assimilated form of Latin com "with, together with" (see com-) + aetas "age" (from PIE root *aiw- "vital force, life; long life, eternity") + adjectival suffix -aneus. Related: Coetaneously.