I agree . It's more likely to be a middle name than a comment on the child's behaviour ! The official Scotlandspeople website also sees it that way , for the index ( which I went through en route to viewing the original image) shows 'George Naughty' as the forenames of the deceased child . I can't however so far find a baptismal record of the child .
The surname Naughty is certainly found in that era and in that part of Scotland . The 1851 Scottish Census shows 45 people with that surname , all but one living in Aberdeen, or in nearby counties . So Naughty might have been a family surname in an earlier generation , or the surname of a close family friend as a tribute to whom the child was given Naughty as a middle name.