My first encounter with the term firewall was back when I worked for an ISP, and it was in the sense used in computer communications. That is, a system that controls the network traffic both into the network and out of the network. Usually the rules that govern network traffic, or access to the network, disallow a lot more than they allow, and thus firewalls are perceived as systems that mostly block access. If this is the firewall you know, and for most tech people it would be, the metaphor that comes to mind is this huge "wall" of raging fire that you can't pass through because, well, you can't walk through fire.
Once I got a little into the history of the term I learned that the original term as used in construction actually refers to a wall supposed to prevent the spread of fire. In some ways this is an even stronger metaphor. It's a barrier that even fire can't pass through.
From construction this term was borrowed to business as one of the alternative terms to Chinese Wall. A firewall in business is the set of rules, regulations etc. that separate, for instance, stock brokers and market traders from people, sometimes even people in the same company, who may have access to confidential information that could influence investments. At some point the term Chinese Wall was considered no longer politically correct, so alternatives were needed, and one of those alternatives is firewall.
Now that firewall had the meaning of preventing information from going through, it was borrowed by the computing field to describe the system that performs a similar task, or rather a task that can be described in similar words, on a computer network.
Once China's Internet censorship policy became common knowledge, it became known as the Great Firewall of China, alluding both to firewall technology, and to the Great Wall of China.
The various terms used to refer to this in Hebrew are interesting.
Wall can be translated in different ways to Hebrew, depending on what kind of wall.
The wall of your house, room, office, etc. is kir.
The wall surrounding a compound, a city (if it's one of those walled cities), and the big one in China is homa (khoma).
In the business/finance sense, the only term used in Hebrew is a direct translation of Chinese wall.
Israel doesn't have a Chinese community, so Chinese just means something or someone from China.
In computer network the term chosen by the Hebrew Language Academy, is homat-esh – that is, not the same kind of wall used in construction, but the other, much bigger kind of wall. I think it is a much better fit than kir, regardless of the ultimate origins of the term. It's much closer to the metaphor envisioned by tech people, for whom the connection of the term to construction is vague and most probably not even known.
This also lends itself nicely to a transparent direct translation of the term the Great Firewall of China, although by itself, I'm sure it was not a consideration, and a single term shouldn't be.
Generally, while etymology may be significant when coining a translation for jargon, I tend to give the dominant metaphor more weight, as it informs us on the how the term is perceived. I discussed this also in my Brief Tutorial on the Translation of Directory (hebrew) where I outlined the various terms used for directories/folders, the issues with each, and my preference.