Eolais mac Biobhsach[1] (alias 'Irish: Eolus' "knowledge", anglicized "Wallis",[2] "Olis" or "Olus"[3] fl.
[1] Eolais was born into a Túath of the Conmaicne settled in present-day south county Leitrim, in the second half of the 9th century.
[10] In the remote mountainous Cuilcagh-Anierin uplands, the oligotrophic lake named "Lough Munter Eolas" marks a borderline between west Cavan and south Leitrim.
[13] O'Donovan claimed the family name (Irish: Ó hEóluis "descendant of Eolais") is still found anglicised as "Olus" or "Olis".
[3] In 1566 two instances of the surname corrupted as "Oelase" and "Olase", are found in the Irish Fiants for Leinster.