Merriam-Webster's Collegiate® Dictionary, 11th Edition
SKINNY
I. adjective (skinnier; -est)
Date: 1573
resembling skin ; membranous ,
2. lacking sufficient flesh ; very thin ; emaciated, lacking usual or desirable bulk, quantity, qualities, or significance, see: lean skinniness noun
II. noun
Etymology: perhaps from 1skin + 4-y
Date: 1938
inside information ; dope