Maximum human lifespan.

[ChetSinger]

Then how do you explain how long this woman lived? https://en.wikipedia.org/wiki/Jeanne_Calment

The ancients commonly rounded numbers. So I don't sweat anyone beating that 120-year limit by a few years.

But many believe that 120-year limit means something else entirely: it was the number of years between God deciding to flood humanity and him actually doing it.

Here's the passage (Gen 6) in the NET bible:

When humankind began to multiply on the face of the earth, and daughters were born to them, the sons of God saw that the daughters of humankind were beautiful. Thus they took wives for themselves from any they chose.

So the Lord said, “My spirit will not remain in humankind indefinitely, since they are mortal. They will remain for 120 more years.”

And here's one of the passage's footnotes:

Heb “his days will be 120 years.” Some interpret this to mean that the age expectancy of people from this point on would be 120, but neither the subsequent narrative nor reality favors this. It is more likely that this refers to the time remaining between this announcement of judgment and the coming of the flood.

After all, there are many post-Flood people in the Bible who lived past 120 years. Abraham lived to 175.