Is presumable related to book, and to tree.

the german for cotton is tree wool.

cotton was imported from china and was a luxury fiber till? (i don't know when!) it still was a luxury fiber as late as 1860!

Latin bombyx, bombycis, 'silkworm; silk; silk garment'; Medieval Latin bombax 'cotton' is a variant of bombyx.

Book is from OE boc, nom pl. bec pronounced [baych]. This is from the PIE root bhago- which also gives us beech, the tree.

Since we're on it: tree, true, trust, druid, and obdurate, amongst a host of others, are from PIE *deru- 'tree'.

Cool!
10. druid, from Latin druides, druids, probably from Celtic compound *dru-wid-, “strong seer” (From zmjezhd's link above.)

tree, true, trust, druid, and obdurate, amongst a host of others, are from PIE *deru- 'tree'. Ooh--and enduring? Trees sure are.

Ooh--and enduring? Trees sure are.

Yes, both from Latin durus 'hard' which the wood of oaks is.