Definition of heart cockle in US English:

heart cockle

noun

  • Any of various bivalve molluscs, the two shell valves of which together form the shape of a heart, especially the large Glossus humanus (family Glossidae) and various relatively large species of the family Cardiidae.

Origin

Early 18th century; earliest use found in James Petiver (c1665–1718), botanist and entomologist.