saddle vs burthen

saddle and burthen both are nouns.

Word	Noun	Adjective	Verb	Adverb
saddle	Yes	No	Yes	No
burthen	Yes	No	Yes	No

As verbs, burthen is a hypernym of saddle; that is, burthen is a word with a broader meaning than saddle:

Other hypernyms of saddle include burden, weight, weight down.

saddle (noun)	burthen (noun)
posterior part of the back of a domestic fowl	a variant of `burden'
a seat for the rider of a horse or other animal
a seat for the rider of a bicycle
a piece of leather across the instep of a shoe
cut of meat (especially mutton or lamb) consisting of part of the backbone and both loins
a pass or ridge that slopes gently between two peaks (is shaped like a saddle)

saddle (verb)	burthen (verb)
impose a task upon, assign a responsibility to	weight down with a load
put a saddle on
load or burden; encumber