In Greek mythology, a giant monster with three bodies or three heads who guarded a herd of cattle; capturing his cattle was one of Hercules' Twelve Labors.
From Greek Geryones; the etymology within Greek is unclear, but likely pre-Greek or related to 'geras' (honor/privilege), suggesting a creature of significance.
Geryon appears in both Greek and Roman mythology with wildly different descriptions—some say three heads, some say three complete bodies, which shows how much mythological details shifted as stories traveled.
Complete word intelligence in one call. Free tier — 50 lookups/day.