Origin of the word "mere"

The word mere comes from Old English mere, meaning a ("lake") or ("pool"). In compound words it could also mean "sea". It is interesting to note how the word, from its earliest root through to present day, has very similar meanings, not only through time but also across a broad spectrum of European countries.

From the original reconstructed Proto-Indo-European root word *móri, which means ("sea") or ("standing water"), the descendants of this word follow the English lineage:
 * Proto-Germanic *mari → sea, ocean, lake, body of water
 * Proto-West-Germanic *mari → sea or lake
 * Old English mere → lake, pool or (compound) sea
 * Middle English mere → lake, pond, pool; also, a sea or an ocean
 * English mere → A body of standing water, such as a lake or a pond. More specifically, it can refer to a lake that is broad in relation to its depth.

It should be noted that Old English mere also corresponds with Old Frisian mere, Old Saxon meri, Old Dutch *meri and Old High German meri. It is cognate with West Frisian mar, Dutch meer, and German Meer. Like the English lineage above, they also derive from the reconstructed Proto-Germanic *mari.

The Proto-Indo-European root *móri spawned similar words in other European languages too:
 * From Latin mare: Italian mare, Spanish mar, French mer, Portuguese mar;
 * From Old Celtic *mori: Irish muir, Welsh môr, Breton mor, Cornish mor, Manx mooir and Scottish Gaelic muir, all of which mean "sea" in various forms. However, in the English lineage, the larger sense of "sea" has been obsolete since Middle English.

Mere in the present instance refers to the names Buttermere, Grasmere, Kentmere, Thirlmere and Windermere, which are recorded from the late 12th or 13th century and would generally mean lake. The term "water" is used more often for the larger of the lakes although this is not strictly so as Blea Water is a tarn and smaller than all of the big lakes, with the exception of Elter Water.

Dictionaries used

 * Anglo-Saxon Dictionary Online
 * Middle English Compendium
 * Wiktionary