Bandwidth
Etymology
From radio engineering, where a signal occupies a "band" of frequencies and its bandwidth was literally the width of that band in hertz. As digital networks grew it came to mean data rate — bits per second. From there it leapt into everyday speech as a metaphor for a person’s spare mental capacity: "I don’t have the bandwidth for this."
noun · /BAND-width/
The maximum rate at which data can move through a connection in a given time.
What it names
It gives us a single number for the width of a pipe — how much can flow at once — which is why the metaphor migrated so easily to human capacity.
Example
Four people streaming video at once ate all the bandwidth, so the call kept freezing.
Related idea
Bandwidth is often confused with latency: bandwidth is how much data fits through per second, while latency is the delay before any of it arrives. A fat pipe with high latency still feels sluggish to click.
noun · /BAND-width/
Figuratively, the mental capacity, energy, or time a person has available.
What it names
how much one can take on at once.
Example
I don’t have the bandwidth to add another project this week.
Related idea
Borrows the data sense — a fixed pipe that can only carry so much.