u/itsallfolklore answered a question about the origin of the commonly accepted pointy elf ears in this AskHistorians post giving good reasons as to what time period the idea might have emerged.

I HIGHLY recommend reading the entire comment but the highlight of it to answer your question would be:

Tolkien did not invent the pointed ears, nor was it an inheritance from medieval literature/art or from the folk themselves (at least in any general way). Pointed ears would defeat the purpose of many of the widespread Northern European legends since they would be a "dead giveaway" of the elfin nature of an encounter, while legends often unfold this truth slowly in the narrative. We need, therefore, to look at the artists who were fulfilling an emerging need for children's literature and a general fascination will all things elfin during the Victorian period.