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"mercury, quicksilver," 1560s, from Latin hydrargyrus, from Greek hydrargyros, from hydr-, stem of hydor "water" (see water (n.1)) + argyros "silver" (see argent). Hence the chemical abbreviation Hg for the element mercury.
hydrargyrum hy·drar·gy·rum (hī-drär'jə-rəm)n. See mercury.