This name is simply an elaboration of Graça ("grace") with the (formerly) popular feminine suffix -ília - present in names like Marília or Idília. "Grácil" isn't even a Portuguese word; "gracious" would be translated as "Graciosa" (which, by the way, is also sometimes found as a name!) [noted -ed]
Sources: https://pt.m.wikipedia.org/wiki/Prefeito_das_provis%C3%B5es (Caio Turrânio Gracílio)