The character 'kuai' in the modern Mandarin name for chopsticks (筷子) is different from the homophone meaning 'fast' (快) - the former has the bamboo radical. (Though perhaps they are related?) I understood the taboo on 'zhu' was related to its similarity to the Imperial surname of the Ming dynasty - emperor's surnames could not be used lightly.

This phonetic similarity has led to another interesting chopstick-related tradition in China though. Newlyweds are presented with a pair, because 'kuaizi' (筷子) sounds like 'have a son soon' (快子). (kuai = 'fast, soon' as mentioned above, 'zi' can be a nominalising suffix as in the word for chopsticks, but the base meaning of the character is 'son'). Sadly, having a son (as opposed to a daughter) is still the ideal for many families here.