The baby name Llewellyn appears in baby name data for the United States from 1910 to 1968. It was most popular in 1918 with 30 babies given the name.
In the later years of this period, Llewellyn has become less common than it once was.
| Year | Count |
|---|---|
| 1910 | 7 |
| 1912 | 8 |
| 1913 | 10 |
| 1914 | 11 |
| 1915 | 15 |
| 1916 | 20 |
| 1917 | 26 |
| 1918 | 30 |
| 1919 | 22 |
| 1920 | 18 |
| 1921 | 24 |
| 1922 | 27 |
| 1923 | 16 |
| 1924 | 19 |
| 1925 | 8 |
| 1926 | 16 |
| 1927 | 13 |
| 1928 | 12 |
| 1929 | 18 |
| 1931 | 6 |
| 1932 | 6 |
| 1933 | 10 |
| 1934 | 5 |
| 1935 | 5 |
| 1936 | 15 |
| 1937 | 16 |
| 1938 | 11 |
| 1940 | 25 |
| 1941 | 6 |
| 1942 | 14 |
| 1944 | 15 |
| 1946 | 11 |
| 1947 | 5 |
| 1948 | 10 |
| 1949 | 24 |
| 1952 | 5 |
| 1954 | 10 |
| 1955 | 5 |
| 1956 | 6 |
| 1957 | 20 |
| 1958 | 6 |
| 1959 | 5 |
| 1960 | 10 |
| 1963 | 5 |
| 1968 | 5 |