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It certainly looks like a Spanish version of the Greek Polyarchos. If there were a Saint Polyarchos that would strengthen the case for this interpretation. However I've found no evidence of a saint so named.
With Filipino surnames ending in -co, you often have an adapted Chinese name, for example Cohuanco, meaning "elder brother Ko Huan". the -co ending is a Chinese honorific, but it can give a surname a Spanish appearance. I can't see Poliarco as an adapted Chinese name, but it's worth bearing in mind.