marine mollusk, cuttlefish, 1610s, of unknown origin; perhaps a sailors' variant of squirt, so called for the "ink" it squirts out.
Entries linking to squid
squirt v.
late 15c., squyrten "to spit" (intransitive), of uncertain origin, probably imitative. Transitive sense "cause to issue in a sudden jet or stream" is from 1580s. Related: Squirted; squirting. Squirt-gun attested from 1803.