Further to my inquiries about the possible name of Caerau prior to it being “Caerau“, I have been informed by a colleague in the Welsh department of Cardiff University that:
“As the form consistently has the ‘d’ I doubt it would be ‘uchel’. If it corresponds to what would be ‘dwygil’ in modern orthography, then it could be ‘dwy’ (‘two’, fem.) + ‘cil’. But ‘cil’ is always masculine as far as I know. But ‘dwy’ is an old variant of ‘duw’, so that’s worth considering. And ‘cil’ can mean ‘source [of a river or stream]’. As ‘dwy’ does occur in river names (as in the name of the River Dee), it’s not impossible that ‘duicil’ could mean ‘source of the ‘’dwy’’ stream’ (cf. Afon Dwyfach, which mean ‘little holy river’). So ‘Fort of the holy stream’s source’ or ‘fort of the holy spring’? I assume there’s a spring up on the hill? But in the compounds I’m aware of which have ‘cil’ + river name, the ‘cil’ element comes first. It’d be good to have an exmaple with ‘cil’ second.”
– private correspondence
There are several springs on Caerau… one on the western end of the fort (Trench 9) and, tellingly, one near the church. We do have suspected ritual activity going on up there throughout the history of the settlement.