I've heard many times from my Rabbeim throughout the years that כרפס is the same letters as ס' פרך, representing the 60 myriads of Jews who were forced to do עבודת פרך (often translated as crushing labor - see Rashi on Shemos 1:13 or with a soft mouth - see beginning of Sotah 11b).
Is there any (preferably early) source that this is where the word כרפס comes from? I've checked many Haggadahs and haven't found that anywhere (I've found other sources for the word Karpas, such as the ones noted here, but I'm looking specifically for a source that it is named that because it is an anagram of ס' פרך.