The names on the post relate to the dungeon that the corresponding helm drops in.
so for example if you have just dropped a monster helm from selenes web & want you wnt the accompanying shoulders this image is a quick & easy reference as to which chest you need to open to have a chance of dropping the shoulders you want.
Don't trust this picture.... these chests have different places in the main cities, for example in Wayrest the left and right chests are switched.
An easier way of choosing which chest to open for is knowing which pledge giver gives which dungeon as a quest.
for example; you're looking for Valkyn Skoria Shoulder piece, Valkyn Skoria drops in City of Ash.
The pledge giver that gives you the quest to go to City of Ash is Gilrion, meaning if you want a Valkyn Skoria Shoulder piece you have to open the chest of Gilrion. (chest on the pic is showing the left one, but in Wayrest Gilrion's chest is the right one when looking at it)
Here is a list, which is also just in the patch notes which pledge giver gives which dungeons:
Maj al-Ragath offers a random Pledge for the following Dungeons:
Banished Cells I & II
Darkshade Caverns I & II
Elden Hollow I & II
Fungal Grotto I & II
Spindleclutch I & II
Wayrest Sewers I & II
Gilirion the Redbeard offers a random Pledge for the following Dungeons:
Arx Corinium
Blackheart Haven
Blessed Crucible
City of Ash I & II
Crypt of Hearts I & II
Direfrost
Selene’s Web
Tempest Island
Vaults of Madness
Volenfell
Urgalarg Chief-bane offers a random Pledge for the following Dungeons:
Cradle of Shadows
Imperial City Prison
Ruins of Mazzatun
White-Gold Tower