Emotion categories are complex and fuzzy concepts that children must learn to identify and differentiate in themselves and others. While prior research has shown that children’s emotion-related vocabulary evolves from broad to narrow as they age, the role of metrics such as word specificity within the development of emotion vocabulary remains under-explored. We use WordNet, a hierarchically-organized lexical database, to study word specificity in interview data collected from children on emotion labeling. We show that as children's age increases, they tend to use increasingly specific emotion words and we also analyze this in the context of concept learning. Further, we show that young children sometimes use words that are typically thought of as not being acquired until an older age, which are selected strategically for the given context. These findings provide new insights into understanding vocabulary and concept learning changes over age that contribute to the learning of fine-grained emotion category labels.