Floating Island Lake near South Lake Tahoe named after floating grassy mats

Floating Island Lake is a forest-rimmed lake west of South Lake Tahoe. This small lake is located between Mount Tallac and Fallen Leaf Lake. Looking westward across the lake from the Floating Island Lake Trail that passes the lake at its eastern shoreline, grassy patches can sometimes be seen at the western shore. Such patches may slough off from the lakeshore and then float around as grassy mats on the surface of the usually quiet lake. The lake was named after such a floating mat, as Mike White explains:

Five-acre Floating Island Lake was named in the late 1800s for a 20-foot diameter, grass- and shrub-covered natural island that at one time sported a thriving conifer. Since that time, several more grassy mats have sloughed off from the lakeshore and floated about the lake […]

Reference and further reading
“Floating Island & Cathedral Lakes” on pages 165 and 166 in Mike White's hiking guide Afoot & Afield • Reno-Tahoe • A comprehensive hiking guide. Wilderness Press, Berkeley, California, 2nd printing November 2008.