Can someone tell me why this wire is here?

Sorry if wrong place. Best I could find. There's a trailer light hookup cable that was installed under the bed cover in my 2017 TRD OffRoad. Does anyone know why this would be here? Bought it used, so might be an addition?

 

Yup, not OEM or someone rerouted it.

 

My used 2014 has an identical plug. I believe it's a different pin configuration for those needing 4 pins instead of 5 for the trailer lights.

 

The previous owner may have had a shell on it? The place that put my shell on asked if i wanted a "quick connect" which let them be lazy and run a trailer extension from the 4 pin up to the shell's brake light

 

Thanks. Shell seems likely. Maybe they traded it for a 4runner.