Q. Why do we call karpas by this name?
A. Though Cecil Roth links the karpas with the bunch of hyssop which, dipped in the blood of the paschal lamb, marked the Israelite houses in Egypt, he does not seem to give a satisfactory explanation of its name.
Others say we have karpas not so much because of what it is (celery, radish, lettuce, potato, onion or parsley) but because of its name:
The Maharil (Rabbi Yom-Tov Lipmann Heller, 1579-1654), points out that the letters of karpas are the same as s-p-r-ch, read Samech (60) Perech – 60 times ten thousand sufferers of toil.
However, karpas is actually a Biblical word found in the Book of Esther, chapter 1, where it denotes a textile.
Rashi uses this word in describing the coat of many colours which Joseph wore (Gen. 37:3) and since the coat was dipped into blood the idea might have developed to dip a vegetable in salt during the Seder.
In a sense this tells us something about how the Egyptian persecution began – by an innocent coat besmirched by blood, symbolic of persecution throughout the ages in which blood was death and not life.