"slender, lithe," 1817, svelt, from French svelte "slim, slender" (17c.), from Italian svelto "slim, slender," originally "pulled out, lengthened," past participle of svellere "to pluck or root out," from Vulgar Latin *exvellere, from Latin ex- "out" (see ex-) + vellere "to pluck, stretch," from PIE *wel-no-, suffixed form of *uelh- "to strike" (source also of Hittite ualh- "to hit, strike," Greek aliskomai "to be caught").
also schlimazel, etc., "born loser, unlucky person," 1948, from Yiddish phrase shlim mazel "rotten luck," from Middle High German slim "crooked" (see slim (adj.)) + Hebrew mazzal "luck" (as in mazel tov). British slang shemozzle "an unhappy plight" (1889) probably is from the same source. Compare schlemiel.
A shlemiel is the fellow who climbs to the top of a ladder with a bucket of paint and then drops it. A shimazl is the fellow on whose head the bucket falls. [Rep. Stephen J. Solarz, D.-N.Y., quoted 1986; there are many and older versions of the quip]