system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why the abbreviation of ounces turned into oz. when there is no letter Z in it?

Where did the letter “z” come from?
gpt
"oz" came from the Spanish "onza" -- meaning ounce. The words "ounce" and "onza" come from the Latin "uncia" meaning "1/12th", because an uncia was 1/12th of a libra (pound). For that matter "lb" for pound comes from "libra".

In the avoirdupois system of measures, there are 16 ounces to a pound rather than 12.