Ailerán (Aileranus Sapiens) (d. 665), fer léigind (lector or chief scholar) of the monastery of Clonard, Co. Meath, died in the great cholera or plague, termed the Buide Conaill (AU 665). His obit is given as 29 December in the Martyrology of Tallaght and in the Martyrology of Óengus (qv) (fl. c.830) – where he is denoted ‘Airerán nÉcnae’ (of the learning or wisdom). Sedulius Scottus (qv) calls him sapientissimus Scottorum, ‘the most learned of the Irish’, in his ‘Collectaneum in Matthaeum’. Sedulius may also have been responsible for some Latin verses in the margin of a Reichenau manuscript in which Ailerán is named among the luminaries of the Irish church beside Finnian (qv) of Clonard and a certain Fergus. In the Latin Life of Féchín (qv) (d. 665) of Fore, a northern contemporary, he is called ‘Ailerán the learned’, and is named as a credible written witness (sapienti uiro Ailerano referente) to certain miracles of Féchín that were performed while he was on a mission to the pagan inhabitants of the island of Omey off the coast of Galway. The second Irish Life of Féchín, partly translated from Latin (1329) by Nicholas the Young, son of the abbot of Cong, quotes some words from what it calls the ‘compendium’ written by ‘Eruran [Ailerán] the sage’ of the life of Féchín. It is possible that this was a compilation of first-hand recollections of the doings of that saint, such as a disciple might compile of his master. No trace of this compendium now exists, and very little either of Ailerán's other hagiographical work.
Ailerán was the author of a learned exposition of the spiritual and moral senses of the names in the genealogy of Christ in Matthew's gospel (Matt. 1, 1–16). His exposition of the Matthaean genealogy of Christ was described by James F. Kenney (qv) as ‘one of the few surviving products of old Irish exegesis’. The text is divided into two parts. The first, the mystical exposition, expounds the meaning of the names of Christ's forebears from Abraham to Joseph according to the mystical or spiritual sense – that is, in so far as they each pertain to the divine and human Persons of Christ, to the foretelling of his birth (Isaac), his mission of teaching and miracles, Passion and death (Joatham), resurrection and Second Coming (Naason), and so forth. In accordance with the universal practice of the Fathers, he adduces testimonia or proof-texts from the psalms, the prophets, and the gospels in support of his exposition. The second and longer part, the moral exposition, draws out the significance and application of the etymologies of each name in so far as they pertain to some facet of Christian life and practice. Thus, taking one example, Manasse relates to the forgiveness of one's neighbour for his or her offences and God's reciprocal forgiveness of one's own offences. It is a remarkably erudite and compact text which provides a valuable insight into the theological understanding and profound learning of a seventh-century Irish savant. It is especially important for its use of a wide range of Greek onomastica sacra that have no currency in any extant Latin onomasticon, and it furnishes evidence of a knowledge of Greek in the early Irish schools. In addition, it shows awareness of numerous patristic sources not yet found elsewhere in Hiberno-Latin literature.
Ailerán also composed a versified exposition in forty-two lines of the numerical structure of the Eusebian canons prefaced to the four gospels in early biblical manuscripts. Eugene O'Curry (qv) has attributed a litany to the Persons of the Trinity (‘Airchís Dín’) in the Yellow Book of Lecan to him, but no manuscript of the text has this attribution, which is based upon an isolated gloss in another manuscript. The famous Old Irish litany, the ‘Scuab Chrábaid’ (besom of [ascetic] devotion), usually attributed to Colgu (qv) grandson of Duinechaid, lector of Clonmacnoise, is also attributed to Ailerán in one manuscript. A tract entitled ‘Rethorica Alerani’, probably some kind of grammatical text, was still in the monastic library of St Florian, near Linz, Austria, up to the twelfth century.
Ailerán is also credited with a number of hagiographical works. An anonymous Latin elegiac poem of the eighth or ninth century and the ninth-century metrical Life of St Brigit (qv) by Donatus (qv) of Fiesole attribute a collection of the miracles of Brigit of Kildare to him; fragments of his Life of Brigit, if such it was, may be preserved in the Latin ‘Vita Prima’ (seventh or eighth century), and in the ninth-century Old Irish ‘Bethu Brigte’. A note added to the ninth-century Tripartite Life of St Patrick (qv) includes him in a list of eight scholars who wrote accounts of Patrick's miracles. John Colgan (qv) credited him with authorship of the fourth Latin Life of Patrick printed in his Triadis thaumaturgae acta (1647). Some of the attributions to Ailerán, however, may have arisen from confusion with the rather similarly named Airfhinnán (d. 803, feast-day 11 August), abbot of Tallaght, with whom Ailerán is sometimes confused in the manuscripts of the martyrologies.