A tedious experience, a bore, as in After several thousand times, signing your autograph can be a drag. This seemingly modern term was army slang during the Civil War. The allusion probably is to drag as something that impedes progress. [Colloquial; mid-1800s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use a drag in a sentence
Slowly nosing his way up the ridge, came a full-grown skunk, his tail a-drag, his head swinging close to the ground.The Face of the Fields | Dallas Lore Sharp