Yes, eta is a Scrabble word!
...and is worth 3 points in Scrabble, and 3 points in Words with Friends
eta
Noun
1. 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
2. The 7th letter of the Greek alphabet
What Scrabble words can I make with the letters in eta?
3 Letter Words
2 Letter Words