I had not heard the phrase “cockles of the heart” in a long time and was recently startled to read it in Map Librarianship by Mary Lynette Larsgaard.
I looked the phrase up in the OED and found a quote by Darwin:
“1858 Darwin in Life & Lett. (1888) II. 112, I have just had the innermost cockles of my heart rejoiced by a letter from Lyell.”
“cockle, n.2″. OED Online. September 2012. Oxford University Press. 19 October 2012.