It was originally associated with St Cairneach, patron saint of Dulane, County Meath,[3] but by the late medieval period had become part of the cult of the abbot and missionary Colm Cille (521-59 AD).

[4] The shrine was heavily re-worked in the 16th century; in 1534 the goldsmith Brian O'Morrison added a front cover and side plates adorned with semi-precious stones, and reliefs including the crucified Christ, depictions of the crowned Virgin and Child, and the three patron saints of Ireland: St. Bridget, St. Patrick and Colm Cille.

[10] Like most cumdachs, a format only found in Ireland and Scotland,[6] it was not designed to be opened but to enclose and protect a relic or text in its chamber,[1] while instilling, according to the art and architecture historian Rachel Moss, "wonder in the observer".

[4] There are late 11th century cast copper alloy plates on each side, decorated with openwork zoomorphic illustrations,[10] whose designs show the influence of the Ringerike style.

He signed the work with an inscription in Latin, which was translated by the Irish artist, antiquary, archaeologist and collector George Petrie as "Briain ua Muirguissan covered me, anno M.CCCCC.XXXIIII".

[20] This can be seen in how the front cover in many 16th-century reworkings, including this work, resemble 10th- and 11th-century illuminated manuscripts and high crosses, in that they are characterised by a surface divided into quadrants separated by raised bands, which the later artists usually made from bronze or silver.

[21] Petrie had a similar view, and considered the other surviving cumdach, the Domnach Airgid, to be of a "purer style of art, and [of] more perfect execution" than the original metalwork on the Miosach shrine.

[23] According to records from an enquiry into the object in 1609, it was then in the townland of Fahan, near the Donegal parish of Clonmany, having been recently obtained from bishop Thomas Barnard of Derry.

Notably, Petrie dismissed Betham's idea that the word "Miosach" is derived from a Hebrew root as "totally absurd and groundless".