Before Spideroak started (ab)using the term in this way, the password manager Clipperz did as well. However, they saw the error of their ways and switched from "zero-knowledge web apps" to "host-proof web apps," which arguably is a better concept. Unfortunately, it never caught on and seems to have died out as Clipperz stopped being actively developed.

Spider Oak has also dropped the term and now goes with "no knowledge."

https://clipperz.is/about/#why-web-cryptography-does-matter

https://en.wikipedia.org/wiki/SpiderOak#History