I've recently been studying etymology and I received a book titled Flappers 2 Rappers: A Study of American Youth Slang written by Dr. Thomas Dalzell. Dr. Dalzell's research goes as far back as the 1850s and one of his entries of that decade is "tight fit" meaning a good joke.
According to http://www.etymonline.com/ the word "killing" meaning extremely funny dates even further back to the 1840s. I understand why a killing is something very funny because when one laughs too hard it causes stomach muscle spasms and shortness of breath, almost restricting the lungs from getting air.
I haven't the least notion why a "tight fit" is a good joke. Any thoughts?