We don't have synonyms for finisg yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are finish, finis and fining.
"He had gone through the work from the title-page to the finis at least forty times, and had just commenced it over again. -- Frederick Marryat, "Mr Midshipman Easy", 1836"
"He had gone through the work from the title-page to the finis at least forty times, and had just commenced it over again. -- Frederick Marryat, "Mr Midshipman Easy", 1836"