Silliness and Wrecklessness

I talked with my oldest daughter about silliness and wrecklessness today. She and her sister were playing too rough at bedtime and the younger slapped the older one pretty hard. It wasn't malicious, they're 4 and 6, they were just being silly but without respect for reality, they were tired, and have been tired for a while (thus the bedtime) and in their silliness and tiredness their actions became wrekless. This is what I explained to her, and she paused and said "Dad, what is wreckless?" and oh man did my heart melt... I'm so proud of her for asking that question, and feeling comfortable to do so in the middle of our conversation made me feel good as her dad.