Greek letter, originally the name of the aspirate, from Phoenician heth.
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Definitions of eta from WordNet
a terrorist organization organized in 1959 by student activists who were dissatisfied with the moderate nationalism of the traditional Basque party; want to create an independent homeland in Spain's western Pyrenees;
Synonyms: Basque Homeland and Freedom / Basque Fatherland and Liberty / Euskadi ta Askatasuna