1670s, "parasite," agent noun from sponge (v.) in figurative sense. As a job on a cannon crew, by 1828.
Entries linking to sponger
sponge v.
late 14c., "to soak up with a sponge," also (transitive) "to cleanse or wipe with a sponge," from sponge (n.). The slang sense of "to live in a parasitic manner, live at the expense of others" is attested from 1670s; sponger (n.) in this sense is from 1670s. Originally it was the victim who was the sponge (c. 1600), because he or she was being "squeezed." Intransitive sense "dive for sponges" is from 1881. Related: Sponged; sponging.