The assimilated form of L. ad- to, before l. In Ofr. reduced to a-, as in alier, for which however al- was often restored as an ‘etymological’ spelling in 14–15th c. in Fr. and Eng. In modern words adopted or formed from Latin the al- is always retained, as allegation, alliterate. Sometimes erroneously for a- in other words as a(l)lay.
