Old English flea, from Proto-Germanic *flauhaz (cf. Old Norse flo, Middle Dutch vlo, German Floh), perhaps related to Old English fleon "to flee," with a notion of "the jumping parasite," or perhaps from PIE *plou- "flea" (cf. Latin pulex, Greek psylla; see puce).
Flea-bag "bed" is from 1839; flea circus is from 1886; flea collar is from 1953.
"A man named 'Mueller' put on the first trained-flea circus in America at the old Stone and Austin museum in Boston nearly forty years ago. Another German named 'Auvershleg' had the first traveling flea circus in this country thirty years ago. In addition to fairs and museums, I get as high as $25 for a private exhibition." ["Professor" William Heckler, quoted in "Popular Mechanics," February 1928. Printed at the top of his programs were "Every action is visible to the naked eye" and "No danger of desertion."]
Any of various small, wingless, bloodsucking insects of the order Siphonaptera that have legs adapted for jumping and are parasitic in the hair and feathers of warm-blooded animals.