Kosei — boys' name

What the Data Says About Kosei

The Social Security Administration has registered 90 babies named Kosei between 2000 and 2020, spanning 21 consecutive years of U.S. birth records. As a boy's name, Kosei currently falls outside the top 1,000 boys' names for 2020. The name reached its historical peak in 2008, when 9 babies received it in a single year.

Decade-level aggregation shows that Kosei performed strongest in the 2010s, accumulating 43 births during that ten-year window. Across the 3 decades of recorded activity, Kosei shows a clear decline from its mid-century high.

No etymological entry is currently available for Kosei in our reference dataset. These figures derive from SSA's annual national and state-level name files, which include any name appearing at least five times in a given year or state-year; names below that threshold are suppressed for privacy and therefore excluded from the totals shown here. The 90 total represents a lower bound — actual usage may be higher in years or states where the count fell below the disclosure floor. This page is provided for informational and research purposes only and does not constitute personal, legal, or naming advice.