Merriam-Webster's Collegiate® Dictionary, 11th Edition
BURDEN
I. noun see: bear Date: before 12th century
1. something that is carried ; load , duty , responsibility , something oppressive or worrisome,
3. the bearing of a load, capacity for carrying cargo , load 11 ,
II. transitive verb (burdened; burdening)
Date: 1541
load , oppress ,
III. noun
Etymology: Middle English burdoun, from Anglo-French burdun a drone bass, of imitative origin
Date: 14th century
a bass or accompanying part,
2. chorus , refrain , a central topic ; theme