Mid 19th century; earliest use found in Anne Baker (1786–1861), philologist. From Molly, pet-form of the female forename Mary + blob: see discussion s.v. mareblob.
Definition of molly-blob in US English:
molly-blob
nounˈmɒliblɒb
English Regional
The marsh marigold, Caltha palustris.
Origin
Mid 19th century; earliest use found in Anne Baker (1786–1861), philologist. From Molly, pet-form of the female forename Mary + blob: see discussion s.v. mareblob.