Correct spelling for the English word "sepion" is [sˈɛpi͡ən], [sˈɛpiən], [s_ˈɛ_p_iə_n] (IPA phonetic alphabet).
There is no widely recognized word "sepion" in the English language. It is possible that you may be referring to a different term or made a typographical error. If you have any other word or term in mind, please let me know and I'll be glad to assist you with its etymology.