I've seen Denault spelled Deneau, Denno, Deno, Denault, Deneault and Denaut so Denio could very well be another variation. Depends upon who the census taker was I guess. My g grandfather, Louis Deno, couldn't read or write English so I can understand how the name became Deno in Fowler, IN in Kankakee, IL it's still Denault. Karen