BURDEN, or Burthen, (1) (A.S. byrthen, from beran, to bear), a load, both literally and figuratively; especially the carrying capacity of a ship; in mining and smelting, the tops or heads of stream-work which lie over the stream of tin, and the proportion of ore and flux to fuel in the charge of a blast-furnace. In Scots and English law the term is applied to an encumbrance on real or personal property. (2) (From the Fr. bourdon, a droning, humming sound) an accompaniment to a song, or the refrain of a song; hence a chief or recurrent topic, as "the burden of a speech."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)