In a complete and detailed way: I'll tell you what happened blow by blow(1930s+)
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 blow by blow
Described in minute detail, as in Tell me about last night's party, blow by blow. This term originated in radio broadcasts during the 1930s, in which the sportscaster gave a detailed account of each punch struck in a boxing match. It soon was transferred to a detailed account of anything at all.