also caddice, larva of the English May-fly, used for bait, 1650s, of unknown origin, perhaps a diminutive of some sense of cad. Also used of the adult stage of certain neuropterous insects.
Entries linking to caddis
cad n.
1730, shortening of cadet (q.v.); originally used of servants, then (1831) of town boys by students at Oxford and English public schools (though at Cambridge it meant "snob"), then "townsman" generally. Compare caddie. The meaning "person lacking in finer feelings" is from 1838.
A cad used to be a jumped-up member of the lower classes who was guilty of behaving as if he didn't know that his lowly origin made him unfit for having sexual relationships with well-bred women. [Anthony West, "H.G. Wells: Aspects of a Life," 1984]