In a reverse process, Old English burthen and murther become burden and murder.
From the en.wikipedia.org
Additional sheathing to the hull added about seven tons to her burthen and perhaps fifteen to her displacement.
From the en.wikipedia.org
She was of 300 tons burthen and had a flush deck.
From the en.wikipedia.org
The woods decay, the woods decay and fall, The vapours weep their burthen to the ground, Man comes and tills the field and lies beneath, And after many a summer dies the swan.
From the guardian.co.uk
More examples
A variant of `burden'
Burden: weight down with a load
Builder's Old Measurement (BOM) is the method of calculating the size or cargo capacity of a ship used in England from approximately 1720 to 1849. The BOM estimated the tonnage of a ship based on length and maximum beam. ...
(obsolete) the tonnage of a ship based on the number of tuns of wine that she could carry in her holds; Archaic spelling of burden; Archaic spelling of burden
A older term used to express a ship's carrying capacity.
The carrying capacity of a vessel, measured in tuns. Gross Burthen is Length x Beam x Depth, divided by 100. Net Burthen is cargo capacity after allowances for space devoted to crew, provisions and miscellaneous storage.