"blanched leaf of artichoke," 1650s, from French carde "chard" (14c.), perhaps via Provençal, from Latin carduus "thistle, artichoke" (see cardoon).
Entries linking to chard
cardoon n.
"artichoke-like plant of the Mediterranean lands," 1610s, from French cardon, from Provençal cardon, properly "thistle," from Late Latin cardonem (nominative cardo) "thistle," related to Latin carduus "thistle, artichoke," which is perhaps from PIE root *kars- "to scrape, scratch" (see harsh (adj.)).