Some French friends of ours own a cottage in Plévenon, near Cap Fréhel. The cottage sits on the edge of the village beyond the church and, on the other side, there is about 1 km of heathland (mostly heather and gorse) between the cottage and the coast.
Their cottage has a Breton name, Pen-ar-Lan.
For a Celtic toponymist this is easy-peasy:
Pen can be derived from Old Breton: penn [Old Cornish: pen/pedn; Welsh: pen], ‘head’, 'end' or 'top’ and Lan comes from Old Breton: lan/n, ‘church site’, ‘monastery' [Welsh: llan; Old Cornish: lan].
So, Pen-ar-lan means that this cottage is simply at the 'end of the church land'.
Or does it?
Our friend insists that lan means heath (as in French: lande).
This would also be an accurate description: the cottage is at the 'end of the heathland'.
And this is where the fun starts.
The Welsh place name element llan is probably the most famous of the Celtic place name elements I have mentioned. This is partly because it is so widespread but also because the 'll-' sound is notoriously difficult for non-Welsh speakers to pronounce. It is, in fact, a voiceless lateral fricative which means that you pronounce an 'l' but allow air to escape from both sides of your tongue.
Llan appears in place names such as Llanelli, Llangollen, Llanberis, Llandudno, Llandewi, Llanwrda and, of course,it appears five times in:
The original meaning of Welsh llan indicated an 'enclosed piece of land', but the word came to imply a 'church' or 'monastery' site or 'parish land' (on which it stood).
This happened in Breton and Cornish too, although the Old Breton: lann still retained a second connotation of '(open) heath.' This is because the etymological roots of 'lan/n' and 'llan' go very deep.
A Proto-Indo-European *lendh, 'land/heath' has been proposed as an original source for its modern variations in hundreds of languages.
From this we can then derive the Proto-Germanic: landom and the Old English: land, 'ground, soil,territory'. These are, in fact, the source of the Old French/French launde/lande and, in turn, the Old French root is the origin of the modern English word lawn.