Ἄτησις

From LSJ

τὸ πλῆθος οὐκ εὐαρίθμητον ἦν → the crowd wasn't easy to count, the crowd was not small, it was not a small crowd

Source

Spanish (DGE)

Atesis afluente del Isarco, río de los Apeninos, actual Adigo, Str.4.6.9.