Origin of prescriptive
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
making or giving directions, rules, or injunctions
sanctioned by long-standing usage or custom
derived from or based upon legal prescriptiona prescriptive title
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
1748, from Late Latin praescriptivus, from praescript-, past participle stem of praescribere (see prescription). Or formed in English from archaic prescript "a direction" (1530s), from Latin praescriptum.
Online Etymology Dictionary, © 2010 Douglas Harper