Here's a text from a Catholic Apologetics site that I think must be a literal translation of whatever Mrs. Alexander was working from. Apparently the Irish title is

FÀETH FIADA

I arise today
in a mighty strength
calling upon the Trinity
believing in the Three Persons
saying they are One
thanking my Creator.

I arise today,
strengthened by Christ's own baptism
made strong by his crucifixion and his burial
made strong by his resurrection and his ascension
made strong by his descent to meet me on the day of doom.

I arise today

strengthened by cherubims' love of God
by obedience of all angels
by service of archangels
by hope in reward of my resurrection
by prayers of the fathers
by predictions of prophets
by preachings of apostles
by the faith of confessors
by shyness of holy virgins:
by deeds of all holy men.

I arise today
through strength in the sky:
light of sun
moon's reflection
dazzle of fire
speed of lightning
wild wind
deep sea
firm earth
hard rock.

I arise today
with God's strength to pilot me:
God's might to uphold me
God's wisdom to guide me
God's eye to look ahead for me
God's ear to hear me
God's word to speak for me
God's hand to defend me
God's way to lie before me
God's shield to protect me
God's host to safeguard me:

against devil's traps
against attraction of sin
against pull of nature
against all who wish me ill
near and far
alone
and in a crowd.

I summon all these powers to protect me -

against ever cruel and wicked powers that stand
against me
body and soul
against false prophet's wild words
against dark ways of heathen
against false laws of heretics
against magic and idolatry
against spells of smiths, witches and wizards
against every false lore that snares body and soul.

Christ protect me today

against poison, against burning
against drowning, against wounding
so that I may come to enjoy your rich reward.

Christ ever with me, Christ before me, Christ behind me
Christ within me, Christ beneath me, Christ above me
Christ to my right side, Christ to my left
Christ in his breadth, Christ in his length, Christ in depth
Christ in the heart of every man who thinks of me
Christ in the mouth of every man who speaks to me
Christ in every eye that sees me
Christ in every ear to hears me.

I arise today

in mighty strength
making in my mouth the Trinity
believing in mind Three Persons
confessing in heart they are One
thanking my Creator.

Salvation is from the Lord
Salvation is from the Lord
Salvation is from Christ
May your salvation
Three Lords
Be always with us.

So, still looking for the Irish text.

Liland