It is not clear if the name Paisley (Passalek in 1296) is British (i.e. P-Celtic) or Gaelic in origin, but, in either scenario, it is a loan-word from Latin basilica, itself from Greek basilikón.
In these languages, this word generally denoted a ‘public hall for secular use’, but with the christianisation of those cultures, these buildings were reused as churches at an early date, and, in the Latin of early Christian Britain and Ireland, basilica was used of any impressive church building. It is this sense which has been loaned into British and Gaelic (baislec ‘church’ in Old Irish). That said, despite the existence of the abbey, there is no other evidence for an early church in the area; moreover, apart from one other example in Wales, the word is not known in place-names in the United Kingdom. The Gaelic form Pàislig has been preserved due to long-standing contact between Glasgow and the Highlands.
For more information on this name visit www.ainmean-aite.org