The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with slow-burn
Slowly increasing anger. It is often put as
do a slow burn, meaning “gradually grow angrier,” as in I did a slow burn when he kept me waiting for three hours. The burn in this idiom comes from burn up in the sense of “make furious.” The term was first cited in 1938 and was closely associated with comedian Edgar Kennedy.