late 14c., blober "a bubble," probably echoic of bubbling water. Original notion of "bubbling, foaming" survives in the figurative meaning "to cry" (c.1400). Meaning "whale fat" first attested 1660s; earlier it was used in ref. to jellyfish (c.1600).
c.1400, prp. adj. from blubber (v.). Originally of fountains, springs, etc.; of weeping, from 1580s.