Etymology: Middle English bom
Date: 14th century
Etymology: perhaps from 4bum
a. of poor quality or nature <bum luck> <bum advice> b. not valid or deserved <a bum check> <a bum rap> c. not pleasant or enjoyable <a bum trip> 2. affected or disabled by damage or injury <a bum knee> III. verb (bummed; bumming) Etymology: probably back-formation from 1bummer Date: 1863 intransitive verb 1. loaf 2. to spend time unemployed and often wandering — often used with around transitive verb to obtain by asking or begging ; cadge <bum a cigarette> IV. noun Etymology: probably short for 1bummer Date: 1864 1. a. one who sponges off others and avoids work b. one who performs a function poorly <called the umpire a bum> c. one whose time is devoted to a recreational activity <a beach bum> <ski bums> 2. vagrant, tramp V. noun Etymology: perhaps from 3bum Date: 1863 a drinking spree ; bender VI. transitive verb Etymology: probably back-formation from 2bummer Date: 1973 disappoint, depress — often used with out <the news really bummed me out>
New Collegiate Dictionary. 2001.