The phrase "existing from" refers to something that has been present or in existence since a specific time or period. There are several synonyms that can be used to replace this phrase, including "originating from," "dating back to," "emanating from," "stemming from," "having existed since," and "tracing back to." Each of these synonyms emphasizes the time frame or period in which something has been present or in existence, lending specificity and detail to the language used. By using these synonyms, writers can create more engaging and descriptive prose that effectively communicates the history and origins of people, places, and things.