An Etymological Dictionary of Astronomy and Astrophysics

The fact of repeating or duplicity.
That part of the data content that can be dropped without any significant loss of the original information.

Etymology (EN): From L. redundantia “an overflowing, excess,” from redundare “to flow back, overflow, be excessive,” from
→ re- “again” + undare “rise in waves,” from unda “a wave.”

Etymology (PE): Afzun-âyi “redundancy, superabounding,” from afzun “more, greater; more ample,” from afzudan “to add, increase” (Mid.Pers. abzudan “to increase, grow;” O.Pers. abijav- “to increase, add to, promote,” from abi-, aiby- “in addition to; to; against” + root jav- “press forward;” Av. gav- “to hasten, drive;” Sk. jav- “to press forward, impel quickly, excite,” javate “hastens”) + âyi verbal noun of ây- present stem of âmadan “to come, arrive, become”
(Av. ay- “to go, to come,” aēiti “goes;” O.Pers. aitiy “goes;” Skt. e- “to come near,” eti “arrival;” L. ire “to go;” Goth. iddja “went,” Lith. eiti “to go;” Rus. idti “to go”).