Unknown is a distinctive girls' name in United States, ranking #5791 in 1998 with 18 recorded births. The name reached its all-time peak in 2009 with 84 births ranking #2334. Since 1996, the popularity has decreased by 66.0%. In 1998, approximately 1 in every 98,161 girls born was named Unknown. STABLE Recent data shows the name is currently stable.