The Trashmaster Title – Secret Title

The Trashmaster Title is a character-bound hidden title added in the Battle for Azeroth expansion. You can permanently unlock the title by completing a few tasks for Jani.

Step 1: Get the cloak: Trashmaster's Mantle

Trashmaster's Mantle has a chance to drop from K.U.-J.0. in Operation: Mechagon.

You can use a Seal of Wartorn Fate for an additional chance to get the cloak when defeating K.U.-J.0. on Mythic difficulty.

Step 2: Complete the achievement: Get Hek'd

To complete Get Hek'd you will have to complete a number of tasks for Jani in Zandalar.

For more info on how to complete this achievement you can check varenne's comment:

Step 3: Find Jani

Horde players can find Jani at 35.4 7.7 in Dazar'alor.

Note: Make sure Jani is not your active Loa. You can change your active Loa by talking to Chronicler Ash'tari at 50.7 35.3 in Dazar'alor.

/way Dazar'alor:Zuldazar 35.4 7.7 Jani

Alliance players can find Jani at 36.2 36.8 in Vol'dun.

/way Vol'dun 36.2 36.8 Jani

Step 4: Speak with Jani

Speak with Jani and complete the quest "I Am the Trashmaster" by giving her the Trashmaster's Mantle cloak.

Completing the quest will permanently unlock the Trashmaster Title for your character. You will also receive a new cloak: Richly Appointed Drape.