c. 1600, "blister or swelling," imitative. Also used for "bubble" (1640s), "protuberance on a cell surface" (1962). Compare blob. "In relation to blob, bleb expresses a smaller swelling" [OED].
Entries linking to bleb
blob n.
"drop, globule," 1725, from a verb meaning "to make or mark with blobs" (early 15c.), which is perhaps related to bubble. The same noun was used 16c. in senses of "a bubble, a blister." Related: Blobby.