"Is acher in gaíth in-nocht..." (Old Irish pronunciation: [is axʲər inʲ ɣaːi̯θʲ iˈn͈oxt]) is an anonymous 9th-century poem in Old Irish.
The poem exists uniquely as a marginal entry in the Stiftsbibliothek MS 904 at the Abbey of St. Gallen in Switzerland, which is a copy of Priscian's Institutiones grammaticae, heavily glossed in Old Irish.
9th century AD, when Viking attacks on Irish monasteries, schools and churches were a regular occurrence.
Irish singer and academic Pádraigín Ní Uallacháin arranged and recorded the poem in Copenhagen after visiting St. Gallen.
It appears on her 2011 Songs of the Scribe studio album.