Lough na Saggart helps - here's a
Google map link The small lake surrounded by scrub - Priest's Lake would be the meaning. Maybe mass was said near here in Penal times - just a guess. This is on the border of Meath & Westmeath and near Collinstown/ Fore etc. There was a corn mill on the river flowing from this, below Brogan's Bridge, though as gradient is not great, can't have been much a flow. You can see it on the
www.osi.ie mapviewer - look at the 25inch or 6inch historic mapping. It appears to be gone now though you might find ruins of the building or remains of the mill race if you looked on the ground.
Whilst one couldn't be certain, it's pretty likely this was the Strillstown Mill referred to as the catchment area of this drainage is small enough. It seems to be in the townland of Glenidan bordering Brownstown. My guess is that Strillstown is/ was a local townland names - a part of Glenidan. It's quite common to find these 'sub townland' names in Ireland and they are often still known locally if you find people who have grown up in that district. Indeed, they are often still considered townlands but not recognised or known officially - the OS often ignored smaller divisions back in the 1840s when townlands were formalised. If I were you, I'd go there and ask about Strillstown and people who lived there. You could well be pleasantly surprised.
Map 2The site of the mill - might be something in the trees here, ruin of kiln maybe
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