The nursery rhyme “London Bridge is Falling Down” includes a line
Iron and steel will bend and bow
To me as a non-native speaker, both “bend” and “bow” evoke essentially the same kind of mental image in this context. Is there a difference which can be put into words? Or are they fully synonymous here, and just combined for the sake of the rhyme?
Writing this I realized that while apparently both words work for iron and steel (perhaps with some artistic liberty?), I'd only bow to a king and bend rays of light using a lens, not the other way round. But I don't know why, except that I'm copying phrases I have read in these contexts. So perhaps an explanation of situations where just one word is appropriate can help point out distinguishing nuances for situations where both are possible.