The Collaborative International Dictionary of English v.0.48:
Slim \Slim\ (sl[i^]m), a. [Compar. Slimmer; superl.
Slimmest.] [Formerly, bad, worthless, weak, slight, awry,
fr. D. slim; akin to G. schlimm, MHG. slimp oblique, awry; of
uncertain origin. The meaning of the English word seems to
have been influenced by slender.]
1. Worthless; bad. [Prov. Eng. & Scot.]
2. Weak; slight; unsubstantial; poor; as, a slim argument.
"That was a slim excuse." --Barrow.
3. Of small diameter or thickness in proportion to the height
or length; slender; as, a slim person; a slim tree.