system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can "Bill" be short for "William"?
gpt
It rhymes. Literally as simple as that.

Nicknames would be stuff that sounded similar, and often rhymed because of our tendency to say cute rhyming stuff to little kids. "Ricky Dicky" "Willy Billy" "Robby Bobby".

Sometimes the nicknames stick, and we get names like Bob, Will and Dick. Not the same as the original names, but close enough to recognize the similarity.