An authoritative book on English spelling, Upward and Davidson (2011, p. 235) states that 'bamboo' comes from the Malay word bambu. It is a bit ironic, then, that the modern Malay for bamboo is buluh; and my Collins Malay dictionary does not even list bambu.
If Malay already had a perfectly good word for bamboo, why did it adopt a new one? And where did buluh come from?
The WordSense.eu Dictionary suggests that buluh is an indigenous word originating from Proto-Malayic, so I guess there must once have been two terms for bamboo in Malay, though buluh seems to be the most commonly used nowadays.
Upward, C., & Davidson, G. (2011). The History of English Spelling. Malden, MA: Wiley-Blackwell.