Now fear is an emotion / feeling and a human would most certainly experience fear as a natural feeling before ever thinking and describing the experience in words, which seems to be a central part of concepts.
Barrett's point is that a person, say in a dark forest at night, experiences a heightened heart rate, their pupils dilate, their hands may get sweaty, but the identification of these feelings as "fear" is culturally conditioned. Another person may experience those same biological cues in another context and identify it as anticipation, anxiety, excitement, etc. "Emotions" are entirely contextual and constructed in the moment as needed on the fly. There is no universal called Fear (in this example) that applies to all people in all places at all times.