which was to be shown or demonstrated (used especially in mathematical proofs).
Origin of Q.E.D.
First recorded in 1810–20, Q.E.D. is from the Latin word quod erat dēmōnstrandum
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for qed
Historical Examples of qed
“QED” was not intelligible to him, but it sounded very well indeed, he thought.For Fortune and Glory
quod erat demonstrandum
Word Origin for QED
(sense 1) Latin: which was to be shown or proved
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
1760, abbreviation of Latin quod erat demonstrandum "which was to be demonstrated."
Online Etymology Dictionary, © 2010 Douglas Harper