ABS and The Bride were blessed by the Holy Ghost to discover this Maronite Parish not too far from their home.
They both fell in love with The Divine Liturgy and with this hymn and it imprinted in their brains rapidly.
Traditional origins
The Greek phrase Trisagion translates as "Thrice Holy" – as in this hymn God is described as holy in three different qualities; Agios o Theosmeans "Holy God".
The hymn is of great antiquity, and perhaps much older than the event assigned by the Greek Menology as connected to its origin. The tradition recounts that during the reign of Theodosius II (408-450) Constantinople was shaken by a violent earthquake, 24 September, and that whilst the people, the emperor and the Patriarch Proclus of Constantinople (434-446) were praying for heavenly assistance, a child was suddenly lifted into midair, to whom all cried out Kyrie eleison ('Lord, have mercy'). The child was then seen to descend again to the earth, and in a loud voice he exhorted the people to pray : 'Holy God, Holy Mighty, Holy Immortal'. After giving this exhortation, the child died.[citation needed]
The hymn was one of the exclamations of the fathers at the Council of Chalcedon (451), and is common not only to all the Greek Oriental liturgies but was used also in the Gallican Liturgy (see Saint Germain of Paris, d. 576), which shows that the hymn is ancient. Some believe it is extremely ancient, perhaps of apostolic-era origin. However this goes against the menology tradition regarding its origin.
The Coptic Orthodox Church and Armenian Apostolic Church believe that the Trisagion originated from Nicodemus. While taking the body of Christ off the cross with Joseph of Arimathea, Nicodemus saw Jesus Christ's eyes open[and then shouted "Holy God, Holy Mighty, Holy Immortal". Traditionally, it is also considered proof that his Divinity did not part from his humanity.
https://en.wikipedia.org/wiki/Trisagion
ABS loves to sing this at The D.L.
https://christhum.wordpress.com/2012/09/03/what-is-aramaic-and-syriac/