beast of burden, An animal, such as a donkey or mule, used for carrying loads.
shoulder the burden, To take on a heavy responsibility or difficult task.
Word Origin
Language
Old English
Original word
byrthen
Originally meant
a load or weight
Background
The word 'burden' comes from the Old English 'byrthen', meaning a load or weight. It has been used in English since before the 12th century to describe both physical loads and metaphorical ones, like responsibilities or worries.