When trying to find synonyms for the phrase "not well known", there are several options that can be used to convey a similar meaning. Some potential options might include "obscure", "unfamiliar", "unknown", "uncommon", "unrecognized", "unnoticed", "undiscovered", or "unpublicized". Each of these words represents a subtly different nuance of the original phrase, but all generally describe something that is not familiar or recognized by a majority of people. These synonyms can be useful in a variety of contexts, from discussing niche topics or individuals to describing obscure locations or historical events.