Catechu

[Geeta Bharathan]

Mabberley: 'Plant Book'
Acacia catechu (catechu, cutch: India)
--heartwood for tanning, dyeing, for treating fishing nets and sails,
medicinal and as masticatory with betel. True khakhi cloth is dyed and
shrunk with it.

Purseglove: 'Tropical crops'
The manufacture of cutch is an ancient industry in India. It is a greyish
resinous substance obtained by boiling chips of heartwood in water and
then evaporating the liquid. The paler form is used for chewing...

Hobson Jobson says the word is derived from Tamil kAsu (?)

--Geeta