That which by the Seder on Pesach we eat "karpas", what does this word actually mean and where does it come from?
According to Jastrow, the word כרפס refers to an umbelliferous plant (one that has stalks branching out from a common stem, forming a flat or curved surface), like parsley or celery. It is not clear what the word's etymology is, or whether or not it is related to its homonym, כרפס, which turns up in Tanakh. That word, appearing in Esther 1:6, refers to a fine fabric, like linen (acc. to HALOT) or cotton (acc. to BDB). It is related to the Aramaic כרפסא and the Arabic كرباس (karbās), both of which derive from the Sanskrit karpāsa and the Greek καρπασος, meaning "cotton plant".
According to Rashi (cf: Genesis 37:3), this word is synonymous with פסים, which appears both as a reference to the clothes that Yaakov gave Yosef, as well as in 2 Samuel 13:18, in reference to the clothes that Tamar was wearing when Amnon sent her away. According to Rabbi Manoach ben Yaakov of Narvona (MT Hilkhot Chametz uMatzah 8:2), the reason that we dip this type of vegetable on erev pesach is to remind ourselves of the dipping of Yosef's coat into blood, which resulted in the servitude of his entire family and their offspring.
Contrary to some answers here, it is actually very clear where the word's etymology comes from. It's Greek, from the word karpos, which literally means vegetable. Remember that the Greek language was somewhat ubiquitous in Israel at the time the haggadah was being written. The word afikomen is also Greek, as attested to in the Gemarah.
I've read some explanations that point out that the Greek word karpos often referred to a raw vegetable and, even more specifically, to a green, leafy vegetable. Thus, the sages wanted to convey that karpas should always be done with an uncooked green, leafy vegetable such as parsley.
To make things short - I think it's just the vegetable's name.
I searched my Haggadot (one of them includes 12 perushim) - nothing. Wikipedia in Hebrew also doesn't explain the name's origin.
The only thing that comes to my head is that expensive fabrics are also called karpas in Meggillat Ester 1:6:
חוּר כַּרְפַּס וּתְכֵלֶת אָחוּז בְּחַבְלֵי בוּץ וְאַרְגָּמָן עַל גְּלִילֵי כֶסֶף וְעַמּוּדֵי שֵׁשׁ מִטּוֹת זָהָב וָכֶסֶף עַל רִצְפַת בַּהַט וָשֵׁשׁ וְדַר וְסֹחָרֶת
Could imply some connection to the plant, but I still think it's just its name.
One last thing, there's a known clue (Remez) in that name. the
ס (Samech) represents (using Gimmatriah) 60 Riboh (10-thousands) of Israelies (men aged 20-60) praticipating in the exodus. The remaining letters of karpas - being
כרפ - can be transposed to
פרכ which hints the 60*10000 Israelies that were forced labour in Egypt.
According to Rabbi Deutch of the Living Torah Museum, כרפס is a kind of wheat. He quoted an Egyptian dictionary.