Argus Panoptes
Ἄργος Πανόπτης
The watchman with a hundred eyes who slept with only half of them at a time.
His name means "the all-seeing one." Hera set him to guard Io, who had been turned into a heifer.
Hermes lulled every one of his eyes to sleep with endless stories and pipe music, then killed him.
Hera gathered up his eyes and set them in the tail of her own bird, the peacock. That is the pattern on a peacock's feathers.
SourcesOvid, Metamorphoses