Dictionary.net

• A district or neighborhood in which disorderly resorts are frequent; - so called in allusion to the red light kept in front of many such resorts at night.

2010 - New Age Dictionary Database
By Oddity Software

• A district or neighborhood in which disorderly resorts are frequent; - so called in allusion to the red light kept in front of many such resorts at night.

1913 - Webster's Revised Unabridged Dictionary
By Noah Webster.