Hiberno-Latin, also called Hisperic Latin, was a playful and learned sort of Latin literature created and spread by Irish monks during the period from the sixth century to the tenth century.

Hiberno-Latin was notable for its curiously learned vocabulary. While neither Hebrew nor Greek were widely known in Europe during this period --- and it is unlikely the Irish monks were fluent themselves --- odd words from these sources, as well as from Celtic sources were added to Latin vocabulary for effect by these authors. It has been suggested that the curiously learned vocabulary of the poems was caused by the monks learning Latin words from dictionaries and glossaries, so as to mix together unfamiliar words with ordinary ones; unlike many others in Western Europe at the time, the Irish monks did not speak a language descended from Latin.

Notable authors whose works contain something of the Hiberno-Latin spirit include St Columba, St Columbanus, and St Adamnan. St Gildas, the Welsh author of the De excidio Britonum, is also credited with the Lorica, or Breastplate, an apotropaic charm against evil that is written in a curiously learned vocabulary; this too probably relates to an education in the Irish styles of Latin. John Scotus Eriugena was probably one of the last Irish authors to write Hiberno-Latin wordplay. St Hildegard of Bingen preserves an unusual Latin vocabulary that was in use in her convent, and which appears in a few of her poems; this invention may also represent the influence of Hiberno-Latin.

The style reaches its peak of obscurity in the Hisperica Famina'\', which means roughly "Western orations," hisperica is a portmanteau word combining Hibernia, Ireland, and Hesperides, the semi-legendary "Western Isles" that may have been inspired by the Azores or the Canary Islands. The coinage is typical of the wordplay used by these authors. A brief excerpt from a poem on the dawn from the Hisperica Famina'' shows the Irish poet decorating his verses with Greek words:

Titaneus olimphium inflamat arotus tabulatum,
thalasicum illustrat uapore flustrum . . .

The titanian star inflames the dwelling places of Olympus, and illuminates the sea's calm with vapour.

On a much more intelligible level, the hymn Altus prosator, a sequence attributed to St Columba, shows many of the features of Hiberno-Latin; the word prosator, the "first sower" meaning creator, refers to God using an unusual neologism. The text of the poem also contains the word iduma, meaning "hands;" this is probably from Hebrew yadaim. The poem is also an extended alphabetical acrostic, another example of the wordplay typical of Hiberno-Latin The beginning of the poem:

Altus *prosator, *vetustus
dierum et ingenitus
erat absque origine
primordii et *crepidine
est et erit in sæcula
sæculorum infinita;
cuï est unigenitus
*Xristus et sanctus spiritus
coæternus in gloria
deitatis perpetua.
Non tres deos *depropimus
sed unum Deum dicimus,
salva fide in personis
tribus gloriosissimis.

High creator, Ancient of Days, and unborn, who was without origin at the beginning and foundation, who was and shall be in infinite aeons; to whom was only begotten Christ, and the Holy Ghost, co-eternal in the everlasting glory of Godhood. We do not propose three gods, but we speak of one God, but in three most glorious Persons.

*Words marked with an asterisk in the Latin text are learned, neologisms, unusually spelled, or unusual in the context they stand.

James Joyce's work Finnegans Wake preserves something of the spirit of Hiberno-Latin in English. In fact, book I, chapter 7 of Finnegans Wake quotes bits of the Altus prosator in an untranslatable Latin passage full of toilet humour.