Yiddish loan words for the foolish & incompetent
Solution 1:
I learned (by usage-N.E. North America) that a schmendrick is a young, inexperienced, incompetent, and generally ineffectual but well-meaning person; A "babe in arms" fool; A "Mark" for a professional gambler.
"Oy (Oh, Dear!), the poor schmendrick didn't realize what he was getting into!"