NoSQL was only ever a marketing term. Things like Mongo are what’s been known as KVSes (Key-Value Stores). Mongo basically just rode a hype wave into extremely large amounts of funding but predating it by at least a decade was libmemcached, which lacks the “relational light” functionality that Mongo added but is a more resilient version of the core concept.

Technologies like Redis actually ended up adding significant innovation but they ended up mostly eschewing the NoSQL term anyway.