Exogenously is a term that describes something that originates from outside of an organism or system. Synonyms for exogenously can include externally, extrinsically, or outwardly. Another option might be superficially, which suggests a surface-level impact without penetrating deeply. Alternately, peripherally implies an effect that is on the edges or fringes of a system, while adventitiously suggests a random or unexpected influence that may be positive or negative. Overall, there are many possible synonyms for exogenously depending on the specific context and nuance of the situation being described.