"Pick up Origin Evidence" is an objective in the sidequest Perfectly Peaceful in Borderlands 2
Head into the Caustic Caverns which are accessible through the Sanctuary Hole. Head into the Oozing Discharge from the entrance of the Caustic Caverns. Follow this path until you find the first refuse pile in front of a fence. Look on it to find the first Peaceful ECHO Recorder
From the first piece of evidence head to the North and make your way into the Infested Warehouse. Once inside go to the middle pillar. Look on the Eastern side to find the second piece of Origin Evidence. Grab it to learn more.
Head on through the Infested Warehouse to the West toward the rock formation in front of you. This will lead you to the Guardian Ruins. Continue to the West through it along the shore or the mine cart tracks. This will lead you to the next piece of Origin Evidence
Turn to the South from the third piece of evidence and head into the next area: Abandoned Mining Site through to the Nether Hive. Once there go to the Southeastern cover and find the door. This will lead to Dahl Deep Core 6. Once inside go to the left and over to the final piece of Origin Evidence by the blood splatter and skeletons