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ἀτειρήεις

From LSJ

Sunt verba voces quibus hunc lenire dolorem possis, magnam morbi deponere partem → Words will avail the wretched mind to ease and much abate the dismal black disease.

Horace, Epistles 1.34

Spanish (DGE)

-εσσα, -εν
infatigable, ἔγχος ἀτειρήεντος ... Δηριαδῆος Nonn.D.35.226.