I loot from battleground blazing brut chest.
I equipped it and it got essenced my spitespark without me wanting it.
I just equipped it to see how skill work
I did not essence it.
Guessing that those are “Blazing Brunt” and " Sprightspark" chest armors for the wizard… Well, when you equip a legendary item, you get to choose what the new item will inherit from the already equipped one, rank, gems, rune, essence… If you didn’t uncheck the essence one, the new item will have the old essence once equipped.
If you do this by mistake, you can always go to any Essence Transfer NPC and change it back, with the “Inherit” options. The first one you get is “[ORIGINAL]”. Not sure whether it works if you haven’t extracted that essence previously, though.