Steps to Reproduce
1. Spawn or find a villager who trades some tool or etc that is delighted.
2. Then see what enchantments are in this item you are going to trade with him.
3. After exchanging with him you will see there are sometimes more enchantments on the item you have traded.
NOTE: This means that depending on when the enchantments are on the item you are switching on, some have not appeared. After making the exchange you will see in your inventory how many enchantments you have in the item