The boundary separating Earth's crust from its upper mantle is called the Mohorovicic discontinuity, or the Moho, for short, in honor of the Croatian seismologist Andrija Mohorovicic.
The University of the State of New York 'Regents High School Examination' . IMAGE: By Davorka Herak and Marijan Herak - Seismological Research Letters; November/December 2007; v. 78; no. 6; p. 671-674; DOI: 10.1785/gssrl.78.6.671, Copyrighted free use, https://commons.wikimedia.org/w/index.php?curid=9360920