Fermented Spider Eye
minecraft:fermented_spider_eye
Obtained by crafting.
How to get it
Crafting (shapeless) 
→
Fermented Spider Eye
Villagers buy this
Wandering Trader · Novice 1 → 
3 Emerald
1 3 Emerald minecraft:fermented_spider_eye
Obtained by crafting.
Fermented Spider Eye
1 3 Emerald