The word svelte is rare in English because of its sv spelling, and the sb in the Spanish equivalent esbelto is only somewhat less rare (there’s esbirro ‘henchman’ and esbozo ‘sketch’, for example). Esbelto/svelte, which means ‘gracefully slender, slim’, was borrowed from Italian svelto, the past participle of the verb svellere ‘to stretch out’. That verb developed from Vulgar Latin *exvellere, where the familiar prefix ex- meant ‘out of’, and Latin vellere meant, with respect to an animal, ‘to pluck, pull out, remove the hair or feathers’.
You may be hard-pressed to think of any relatives, but if I tell you the past participle of Latin vellere was vulsus, you can easily see the relationship to the familiar words convulsar/convulse and revulsión/revulsion. There’s also the less-common evulsión/evulsion, which means ‘the act of plucking out’, and which contains the same two semantic elements found in esbelto/svelte. It’s fair to say that some people find evulsion a cause of revulsion.
© 2015 Steven Schwartzman