Why does 負 also mean "minus" and "negative"?
I think it's a mistake to rely too heavily on the glyph origin to interpret meanings of a Chinese morpheme.

It's easy to confuse the origins of Chinese characters and the origins of Chinese words. One is a question about a writing system; the other is a question about etymology and of (primarily spoken) language. In this particular case, the original word pre-dates the entire Chinese writing system. In fact, it can be traced back to before Chinese and Tibetan split! There is still a cognate word meaning &quot;to carry&quot; in Tibetan today. So, the original meaning was &quot;to carry&quot;, and the character was invented to convey that meaning. The use of money in that depiction is presumably incidental.

Even when characters make sense when they're invented, language continues to change. No one goes back and changes the character to match. In this case, I would propose the following chain of meanings:



To (literally) carry something
To (metaphorically) shoulder something, e.g., a burden
To owe, e.g., a debt
Negative number (e.g., a debt on a ledger)

Perhaps that chain of meanings is chronologically incorrect. But if so, the right way to answer the question is to start with the original meaning (&quot;to carry&quot;) and trace (through literary sources) when the other usages came about and in which order they did so. The original construction of the character is only really helpful in terms of understanding the original meaning, not the subsequent chain of extended meanings.