As nouns the difference between packcloth and sackcloth
is that packcloth is a strong, coarse cloth used for packaging while sackcloth is a coarse hessian style of cloth used to make sacks.
packcloth
English
Noun
(-)
A strong, coarse cloth used for packaging
sackcloth
English
Noun
(
en noun)
A coarse hessian style of cloth used to make sacks.
(Usually paired with 'ashes'), garments worn as an act of penance. Now often used figuratively.
- After he realised the gravity of his crime he spent some time wearing sackcloth and ashes.
References
* OED2