Question: Who is Fíachu Finnolach's paternal grandfather?

Knowledge 1: Fíachu Finnolach
Fiacha Finnolach, son of Feradach Finnfechtnach, was, according to medieval Irish legend and historical tradition, a High King of Ireland.He took power after killing his predecessor, Fíatach Finn.He ruled for fifteen, seventeen, or twenty-seven years, depending on the source consulted, after which he, and the freemen of Ireland, were killed in an uprising of "aithech-tuatha" or "subject peoples", led, according to the "Lebor Gabála Érenn" and the "Annals of the Four Masters", by Elim mac Conrach, or by Cairbre Cinnchait according to Geoffrey Keating.His wife Eithne, daughter of the king of Alba (Scotland), who was pregnant, fled home to Alba, where she gave birth to Fíachu's son, Tuathal Techtmar, who would ultimately return to Ireland to claim the throne.The "Lebor Gabála Érenn" synchronises his reign with that of the Roman emperor Nerva (AD 96–98).The chronology of Geoffrey Keating's "Foras Feasa ar Éirinn" dates his reign to AD 28–55, that of the "Annals of the Four Masters" to AD 39–56. [SEP] Knowledge 2: Feradach Finnfechtnach
Feradach Finnfechtnach (modern spelling:Fearadhach Fionnfeachtnach - "fair-blessed"), son of Crimthann Nia Náir, was, according to medieval Irish legend and historical tradition, a High King of Ireland.There is some disagreement in the sources over his position in the traditional sequence of High Kings.The "Lebor Gabála Érenn" and the "Annals of the Four Masters" agree that he came to power after the death of Cairbre Cinnchait.The "Annals" say that when Cairbre overthrew his father, his mother, Baine, daughter of the king of Alba, was pregnant with him, but this would make him less than five years old when he came to the throne: it is likely this is a doublet of a similar story told of the later High King Tuathal Techtmar.The "Annals" also add that Ireland was fertile during his reign, contrasting it with the barren reign of the usurper Cairbre.Geoffrey Keating has Feradach succeed his father Crimthann, placing Cairbre's reign later.Keating relates that the judge Morann mac Máin (who in the "Lebor Gabála" and the "Annals" is the son of Cairbre and his wife Mani) lived in Feradach's time.Morann owned the "id Morainn" (Morann's collar or torc) which would contract around the neck of a judge who made an unjust judgement until he made a just one, or of a witness who made a false testimony until he told the truth.Feradach ruled for twenty years according to the "Lebor Gabála" and Keating, twenty-two according to the "Annals", before dying a natural death at Liathdroim, an ancient name for the Hill of Tara.In all sources he was succeeded by Fíatach Finn.The "Lebor Gabála" synchronises his reign with that of the Roman emperor Domitian (AD 81–96) and the death of Pope Clement I (AD 99).The chronology of Keating's "Foras Feasa ar Éirinn" dates his reign to AD 5–25, that of the "Annals of the Four Masters" to AD 14–36.
Knowledge 1: Fíachu Finnolach
Fiacha Finnolach, son of Feradach Finnfechtnach, was, according to medieval Irish legend and historical tradition, a High King of Ireland.He took power after killing his predecessor, Fíatach Finn.He ruled for fifteen, seventeen, or twenty-seven years, depending on the source consulted, after which he, and the freemen of Ireland, were killed in an uprising of "aithech-tuatha" or "subject peoples", led, according to the "Lebor Gabála Érenn" and the "Annals of the Four Masters", by Elim mac Conrach, or by Cairbre Cinnchait according to Geoffrey Keating.His wife Eithne, daughter of the king of Alba (Scotland), who was pregnant, fled home to Alba, where she gave birth to Fíachu's son, Tuathal Techtmar, who would ultimately return to Ireland to claim the throne.The "Lebor Gabála Érenn" synchronises his reign with that of the Roman emperor Nerva (AD 96–98).The chronology of Geoffrey Keating's "Foras Feasa ar Éirinn" dates his reign to AD 28–55, that of the "Annals of the Four Masters" to AD 39–56. [SEP] Knowledge 2: Fujiwara no Nagara
, also known as Fujiwara no Nagayoshi, was a Japanese statesman, courtier and politician of the early Heian period.He was the grandfather of Emperor Yōzei.
Knowledge 1: Fíachu Finnolach
Fiacha Finnolach, son of Feradach Finnfechtnach, was, according to medieval Irish legend and historical tradition, a High King of Ireland.He took power after killing his predecessor, Fíatach Finn.He ruled for fifteen, seventeen, or twenty-seven years, depending on the source consulted, after which he, and the freemen of Ireland, were killed in an uprising of "aithech-tuatha" or "subject peoples", led, according to the "Lebor Gabála Érenn" and the "Annals of the Four Masters", by Elim mac Conrach, or by Cairbre Cinnchait according to Geoffrey Keating.His wife Eithne, daughter of the king of Alba (Scotland), who was pregnant, fled home to Alba, where she gave birth to Fíachu's son, Tuathal Techtmar, who would ultimately return to Ireland to claim the throne.The "Lebor Gabála Érenn" synchronises his reign with that of the Roman emperor Nerva (AD 96–98).The chronology of Geoffrey Keating's "Foras Feasa ar Éirinn" dates his reign to AD 28–55, that of the "Annals of the Four Masters" to AD 39–56. [SEP] Knowledge 2: Túathal Techtmar
Túathal Techtmar(" the legitimate"), son of Fíachu Finnolach, was a High King of Ireland, according to medieval Irish legend and historical tradition.He is said to be the ancestor of the Uí Néill and Connachta dynasties through his grandson Conn of the Hundred Battles.The name may also have originally referred to an eponymous deity, possibly even a local version of the Gaulish Toutatis.

Answer: Crimthann Nia Náir