compliments of google,
this might answer your question.
Cherries grow on trees, of course, and picking them, done in part from above the tree, can be tricky. Since about 1945, "cherry-picker" in a literal sense has meant the type of mobile hydraulic crane now often used by utility crews working on poles. "Cherry-picking," however, is also a figurative reference to the laborious (and usually at least somewhat selective) process of picking each cherry by hand. "Cherry-picker," meaning a person who picks only the best or easiest opportunities, first appeared a railroad slang in 1940. The verb "to cherry-pick" is much more recent, dating to about 1966.