This is useful context, but given that you're saying "delta" was in use over a decade ago and that you don't have any firsthand knowledge in the time since, it

This is useful context, but given that you're saying "delta" was in use over a decade ago and that you don't have any firsthand knowledge in the time since, it seems at least a little presumptuous to confidently asset that people didn't start colloquially saying "force" afterwards.