The earliest porches were those of the early Christian basilica churches; they were long and arcaded and were called "narthex."
"Our Homeland Churches and How to Study Them"
Sidney Heath
The long aisles and nave of the Roman and early Christian basilicas were replaced by a more or less square plan, lofty piers spanned by arches upholding the central cupola, whilst the galleries above the aisles rested on slender columns such as were also employed to rail off the sanctuary and narthex from the main body of the building.
"Architecture"
Nancy R E Meugens Bell
The general plan is square, but a fine narthex consisting of two spacious halls one above the other projects slightly beyond the actual church at the western end.
"Architecture"
Nancy R E Meugens Bell