I got this when switching classes to something I hadn't leveled yet. Meanwhile as marauder I always get spammed with "your axe now feels like an extension of your body"
For Marauder that's a class ability called "Steadfast". It raises your parry rate a little bit when you sit still in one spot for a few seconds (it gives you a little buff icon too). Unfortunately it seems a little buggy right now because if anything moves you even a tiny bit (like another player or mob running into you and shifting your model) the buff resets.
Steadfast in addition to raising your parry rate also gives other attacks extra benefits like changing Skull Sunder from a single-target attack to a frontal cone attack. I've seen "steadfast" mentioned in tooltips ever since early CB, but I always thought it was a triggered ability that Marauder learned later until one day I used Skull Sunder and ended up striking three mobs with it. Those mobs beat a powerful lesson into my delicate body that day that I'll never forget.
SE needs to label icons in addition to telling you what they do.