History of "novelty" to refer to dessert items
Solution 1:
Etymonline suggests that novelty:
sense of "useless but decorative or amusing object" is attested by 1888 (as in novelty shop, by 1893).
from which by extension it was probably used also to refer to packaged ice creams, something really new for those days.
The following extract is from The National Druggist (1916)
But the point remains that if a lady or a child would rather have an attractive ice cream novelty than the same quantity of cream served in a cone-shaped mass, it may be that there is an opportunity here to attract some business ...