The word lewd shares a similar semantic development with the word vulgar. Both originally referred to common or ordinary people. In the case of lewd, the word originally meant lay, as in a person not in holy orders.
Lewd appears as early as c.890 in an English translation of Bede’s Ecclesiastical History of the English People, which was originally written in Latin:
Þara manna sum wæs...bescoren preost, sum wes læwde sum wæs wifmon.
(One of the people was...a tonsured priest, one was lewd, one was a women.)
By the 13th century, lewd had taken on the meaning of unlearned or illiterate. From Þe Liflade of St. Juliana, written sometime before 1225:
Alle lewede men þat understonden ne mahen latines ledene.
(All lewd men that are not able to understand the language of Latin.)
By the end of the 14th century, the modern sense of lascivious or lustful had developed. A transitional sense can be seen in Chaucer’s c.1386 The Miller’s Prologue:
Lat be thy lewed dronken harlotrye.
(Be done with your lewd, drunken harlotry.)
Note that harlotrye here could mean buffoonery as much as lasciviousness. But by a few decades later, the modern sense had clearly developed. From the c.1430 poem Freemasonry:
In holy churche lef nyse wordes Of lewed speche, and fowle wordes.
(In holy church leave nice words of lewd speech, and foul words.)
(Source: Oxford English Dictionary)
Copyright 1997-2015, by David Wilton