The name is derived from the Livonian element, ilo, meaning “joy.” The name appears in the Chronicle of Henry of Livonia, in the form of the latinized, Ylo. The name was derived in the 19th-century.
It can also be associated with the modern Estonian words, ülev (exalted) and üllas (noble).
Other forms of the name include:
The designated name-day is September 1.