() is an Irish male name meaning [ruling with] 'fervour over the people' or 'valour of the tribe', from Old Irish 'people, tribe, tribal territory' + 'ardour, valour', from Proto-Celtic 'might, ability'.
is also the Modern Irish for movement anticlockwise or widdershins, from the Old Irish 'left, north' + 'turn', from a different Proto-Celtic root not meaning 'people, tribe', see there, sense 2 for details.
People with the name include: Túathal Techtmar, legendary king Túathal Máelgarb (fl. 6th century), king of Tara Túathal mac Máele-Brigte (died 854), king of Leinster Tuathal Mac Augaire (died 958), king of Leinster Túathal (bishop of the Scots) (fl. 1050s), bishop of Cennrígmonaid, modern St Andrews Tuathal Ua Connachtaig (fl. 12th century) Irish bishop of Kells or Breifne
The surname O'Toole is an anglicisation of (), meaning grandson or descendant of Túathal. One instance is the O'Toole family prominent in medieval Wicklow, who claimed descent from Tuathal Mac Augaire.
Placenames associated with the name include: Listowel () 'Túathal's ringfort', a town in County Kerry Carrauntoohil () 'Túathal's sickle', a mountain in County Kerry Glasthule () 'Túathal's stream', a suburb of Dublin
See also List of Irish-language given names Túathalán (died 749), abbot of Cennrígmonaid, modern St Andrews