What is "secundinus"

Saint Secundinus (fl. 5th century), or Sechnall (Modern Irish: Seachnall) as he was known in Irish, was founder and patron saint of Domnach Sechnaill, now Dunshaughlin (Co. Meath), who went down in medieval tradition as a disciple of St Patrick and one of the first bishops of Armagh. Historians have suggested, however, that the connection with St Patrick was a later tradition invented by Armagh historians in favour of their patron saint and that Secundinus is more likely to have been a separate missionary, possibly a companion of Palladius.