And definitely use some corruption of words and vowel shifts. If'n ye looke a' hawe peupel speel'd wordes e'en back'n yon 16eeth an' earlieur centuries, ye shouldst beget ane understaendin' off wha' couldst comme aboot.

Don't overdo it, of course. But it's a classic move for post-apocalyptic settings. Take current names and corrupt away, e.g. San Francisco -- > Freescoe, London -- > Lun Din, Berlin -- > Burrleyn, etc. etc. ...