Tightening / hard bump question... same as braxton hicks?

FTM question... Is having a tight/ hard bump the same as contractions or BH or something entirely different?

I’m 36 weeks along and out of no where my baby bump will get rock hard. It doesn’t feel the same as the Braxton Hicks I got earlier in pregnancy which felt more like a crunch (like exercise) than hardening. And they don’t pass quickly like contractions. The hardening feeling doesn’t hurt at all sticks around for a few minutes.