The process for creating galvanized wrought iron was created in the mid 18th century, long after the time setting of this movie.
When Francis tells Cid that he is going to help him slay the Jabberwock, Cid tells him that he is sadistic. "Sadistic" was named after the Marquis deSade who lived a few hundred years later, therefore the word was not yet in use.
"Jabberwocky" as a word was created in 1872 by Lewis Carroll, yet the word and parts of the Jabberwocky poem are supposedly referenced in a medieval village.