long chalk="long shot" ?

[Douglas G. Wilson]

>Still, I wonder if they are the same phrase?

What is the underlying sense of "shot" or "chalk" here? If "long shot"
basically meant "long odds" (i.e."unlikely") then it's hard to relate
"shot" to "odds" at a glance. If "long chalk" meant "long odds" one might
speculate that the original reference was to odds posted on a chalkboard at
a horse race or something like that. If I had the online OED I'd look these
up there.

-- Doug Wilson