Unknown is a distinctive girls' name in United States, ranking #4436 in 1999 with 26 recorded births. The name reached its all-time peak in 2009 with 84 births ranking #2334. Since 1996, the popularity has decreased by 50.9%. In 1999, approximately 1 in every 68,222 girls born was named Unknown. STABLE Recent data shows the name is currently stable.