The dictionary detective in me was stirred into action by your question about the "cockles of one's heart", and here's the low-down I've found so far:

"… it is astonishing that anatomists of the seventeenth century were already likening the human heart to the shape and valves of the mollusk, common on European shores, and the cockle. That is to say, they saw sufficient resemblance between the two valves of the mollusk and the two ventricles of the heart to refer to the latter as the cockles. Thus, because the heart was long supposed to be the seat of the affections, men spoke of delighting, of rejoicing, of pleasing, and, more recently, of warming the cockles of one's heart." "
From "2107 Curious Word Origins, Sayings & Expressions from White Elephants to a Song and Dance" by Charles Earle Funk (Galahad Book, New York, 1993).

On the other hand:
"Cockles of the heart have nothing to do with the cockles and mussels Sweet Molly Malone used to sell. The word comes from the Latin phrase 'cochleae cordis,' meaning 'ventricles of the heart,' while the shellfish 'cockle' comes from the Latin 'conchylium,' meaning 'conch shell.'"
From "Morris Dictionary of Word and Phrase Origins" by William and Mary Morris (HarperCollins, New York, 1977, 1988).

PS - is it me, or is it odd how Jim keeps on demanding apologies for anything that could even slightly be seen as calling the judgement of the mods into question? But at the same time he's seemingly unaware that the blatant rudeness of some of his own observations (e.g. the "can't you read?" type of jibe) really do deserve to be apologised for.