In Ireland, we are adding townlands based on some old GSGS sheets. Read more here

As well as townlands, these are great for adding names of features, such as lakes. Overpass Turbo can help with this.

If you go to this Overpass page and zoom to an area and press “run”, it will show you all unnamed lakes. Then “Export”, then “JOSM”. It’ll have opened up those unnamed lakes in your JOSM. Use the GSGS maps to add the name (and “water=lake” as appropriate). You don’t need to download any extra data. Upload when done!

It’s surprising how many unnamed lakes there are in OSM, and this can help you really knock some off.

I use JOSM’s filter feature, with the query “name=* and water=*” to hide lakes that I’ve already named. This makes it easier to work through the items.