A
latin phrase meaning literally
"The sweet part in the end". It is often used metaphorically to mean "to top it all".
It is widely known, maybe because it was a ribald goliardic joke probably spread in post-Renaissance Europe by travelling students: "Dulcis in fundo (vaginae)" (that means exactly what it looks like, or "The sweet part is in the end of vagina").
Now this jocular meaning is almost forgotten and the phrase is used only to give your words a touch of latin charme.