As nouns the difference between underback and underbark
is that underback is (brewing) a vessel that receives the wort as it flows from the mashing tub while underbark is the inner layer of tree bark, beneath the overbark.
underback
English
Noun
(
en noun)
(brewing) A vessel that receives the wort as it flows from the mashing tub.
underbark
English
Noun
(-)
The inner layer of tree bark, beneath the overbark.