one of the previous links points out that one of the things that "st patrick" is known for, apocryphally or not, is putting the sun in the celtic cross.

if st patrick's day is essentially a glossed over spring equinox festival, it makes sense that they would have retained the symbolism of the sun.

what they would have been celebrating is the return of the sun for another year - the moment the days get longer again. 

we might not have the narrative, it may have been burned - unless it's hiding deep in one of those hibernian monasteries, waiting to be refound. or maybe buried somewhere deep in an icelandic glacier, waiting to be uncovered as the climate changes. it may even be in some underground tunnel under the vatican, hidden underground to be never found again.

but, i think we can figure this out, can't we?

it's the sun. it's back! hooray!