Old English alewe "fragrant resin of an East Indian tree," a Biblical usage, from Latin aloe, from Greek aloe, translating Hebrew ahalim (plural, perhaps ultimately from a Dravidian language).
The Greek word probably was chosen for resemblance of sound to the Hebrew, because the Greek and Latin words referred originally to a genus of plants with spiky flowers and bitter juice, used as a purgative drug, a sense which appeared in English late 14c. The word was then misapplied to the American agave plant in 1680s. The "true aloe" consequently is called aloe vera.