[German Kieselguhr, obsolete spelling of Kieselgur : Kiesel, pebble (from Middle High German kisel, from Old High German kisil, from Germanic *kisilaz : Germanic *kis-, gravel; probably akin to Lithuanian žiezdra, grain of sand + Germanic *-ilaz, diminutive suffix) + Gur, Guhr, ferment, earthy deposit from water (from gären, to ferment, blend of Middle High German jësan, from Old High German and Middle High German *jern, to cause to ferment, from Old High German jerian; see yes- in the Appendix of Indo-European roots).]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.