The lake's origins relate directly to the last glacial period and the effects of a glacially eroded valley that possibly linked Bassenthwaite Lake with that of Derwentwater as one much larger body of water, seen similarly with Buttermere and Crummock Water. Today, they are connected only by the River Derwent, which meanders through the long-ago silted up alluvial plain that separates the two lakes. It is the only body of water in the Lake District with the word lake in its title. Every other lake uses either mere or water.
Etymology
The name Bassenthwaite means Bastun's clearing where Bassen comes from the Anglo-French surname Bastun, which originally meant stick, and thwaite is related to Old Norse þveit meaning a clearing or more accurately, forest land cleared for agriculture or habitation.[1] The lake took its name from the village of Bassenthwaite.
The name of this lake has changed several times since the Middle Ages. In 1279 it was known as Bastantheweyt, in a period when the Plantaganet Edward I was king of England. In 1539 it was known as Bassyntwater and in 1675 it went by the name of Bassenthaitlake.[2] The similarities and subtle shifts in these names changed when in the late 18th century the name Broad Water or Broadwater was used. This was the name also used for Brothers Water, probably used interchangeably for a period of time until the current name settled.
Name shift
How the name shifted back to the more familiar Bassenthwaite probably came about after the development of the Cockermouth, Keswick and Penrith railway line with the newly constructed "Bassenthwaite Lake Station", built on the northwestern side of the lake next to the hamlet of Dubwath, roughly three miles away from Bassenthwaite village. Over time with continued public use, both Broadwater and Bassenthwaite Lake would have been used interchangeably for a long time for the shift from to the other to realistically happen. Today, Bassenthwaite Lake Station, previously left to ruin, has been thoroughly restored and now serves as a café with a full-sized replica of a French SNCF Class 241 steam engine, where passengers would have once alighted. The fast-moving thoroughfare of the A66 now stands in the footprint, at least in part, of the original railway line.