I can answer your second question.
Polyseme (they share etymologies)
Bank (theme: security)
1. a financial institution
2. a synonym for 'rely upon' (e.g. "I'm your friend, you can bank on me").
Homonym with 1. and 2. above (they do not share etymologies)
1. river bank
It is a completely different meaning. River bed, though, is polysemous with the beds on which people sleep.
Polysemy - Wikipedia, the free encyclopedia