cockle:  The cockle is related etymologically to another mollusc, the conch: they both began life in Greek kónkhē – which meant ‘mussel’ as well as ‘conch’. From this was formed the diminutive konkhúlion ‘small variety of conch’ – hence ‘cockle’. The Greek word subsequently became reduced to kokhúlion, whose plural passed into medieval Latin as *cochilia.
Next in the chain was Old French coquille, source of the English word. The origin of the phrase cockles of one’s heart (first recorded in the mid 17th century) are not clear: some have claimed that the heart resembles a cockle shell, or more specifically that the fibres of the heart muscle spiral like the lines on a cockle shell, while others note a supposed resemblance of cockle to corculum, a Latin diminutive of cor ‘heart’, and others again point out that the scientific name for the cockle is Cardium, from Greek kardíā ‘heart’, but none of these explanations really carries conviction. => conch
type of mollusk, early 14c., from Old French coquille (13c.) "scallop, scallop shell; mother of pearl; a kind of hat," altered (by influence of coque "shell") from Vulgar Latin *conchilia, from Latin conchylium "mussel, shellfish," from Greek konkhylion "little shellfish," from konkhe "mussel, conch." Phrase cockles of the heart (1660s) is perhaps from similar shape, or from Latin corculum, diminutive of cor "heart."
flowering weed that grows in wheat fields, Old English coccel "darnel," used in Middle English to translate the Bible word now usually given as tares (see tare (n.1)). It is in no other Germanic language and may be from a diminutive of Latin coccus "grain, berry."