In Japanese, we don't use "c" in this context so I am assuming you actually meant "dekameron."
Dekai is a colloquial or informal adjective word for "big" or "huge". Normally, this word is used by males, not females. ("i" is dropped to make one word with the following noun). Meron menas melon (as Japanese has no "l" sound). So this literally means a big melon or big melons.
But melons are also often referred to women's breast (informally and colloquially by men). So I think you can guess what it means.
P.S. Just for my curiosity, I found on the internet, "decameron" is some collection of Italian novels:
September 30, 2008
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