It says Portlaoise.
The original Ogham alphabet, the ‘core’, was created to represent Common Insular Celtic or Primitive Irish (or some stage in between the two), at which stage there was no /p/ – the closest value in what would become Irish was /kʷ/, which is why the earliest loan words with [p] ended up having /k/ in Irish.
Later on, after /kʷ/ had merged with /k/, the new phoneme /p/ started appearing in loan words, especially from Latin (but also from Brythonic, where /kʷ/ had merged with /p/ instead). So now a letter for /p/ was needed. The general belief now is that the result was the letter ᚘ, which was probably originally named pín (for Latin pinus ‘pine tree’ – remember that Ogham letters generally have tree names). This is the letter used in the Ogham inscription in your pictures. It is considered one of the forfeda or ‘supplementary’ letters that are not part of the core alphabet, but nonetheless were in somewhat frequent use.
Later on (but still early on in Old Irish), there arose a sort of ‘systematicist’ practice which held that the forfeda should all represent diphthongs, and pín came to be used for /ia/. Why exactly that happened, or why /ia/ in particular, no one knows, but when it did happen, the letter was transparently called iphín (‘i’-pín) because it was ‘the i-like usage of pín’. Later on, when the original use as /p/ and the name pín were lost altogether, so was the transparency of the name iphín, and it started being spelt ifín, which is the common spelling now.
Of course, using pín for /ia/ created a new hole in the alphabet which yet again had no letter for /p/. The solution this time was to take ᚁ beith /b/ and tweak it by rotating it 90°, yielding ᚚ peith(e) or beithe bog ‘soft b’.
The decision to use the very archaic pín to represent /p/ in the Port Laoise sign is somewhat unusual – particularly considering that the name is being rendered in the modern Irish spelling, using separate Ogham letters for ⟨a-o-i⟩, which in Primitive Irish would have looked completely different.
