Originally a Hebrew word, popularized in English by the
cartoonist Herb Gardner. A `sad sack,' a loser, a person who can't make any thing or any situation work right for him or her; unassertive, shy, timid. Reference: `The Joys of Yiddish,' by Leo Rosten. His
definition is "An innocuous, ineffectual, weak, helpless or hapless
unfortunate." There are other spellings also.