Kit gun, a gun that went in your uniform bag, duffle, or foot locker, etc. S&W hijacked the name.
Being lazy, I googled kit - an 18th century English slang term for "outfit" or "collection," as in a soldier's "kit bag," which contained all his worldly possessions. "Kit" may have come from "kith," meaning "estate,"
Also
www.soccerkits.com for football outfits, etc.
Pack up your troubles in your old kit bag and smile, smile, smile.
- from the 1915 English marching song by George Henry Powell.
The chorus goes:
Pack up your troubles in your old kit-bag,
And smile, smile, smile,
While you've a Lucifer to light your fag,
Smile, boys, that's the style.
What's the use of worrying?
It never was worth while, so
Pack up your troubles in your old kit-bag,
And smile, smile, smile.