Being such a prominent mountain near Peter Lassen's property holdings, it does not come as a surprise that this volcano—now the eminent landmark and climber's attraction of Lassen Volcanic National Park—became finally named for the Danish-Mexican blacksmith-rancher. However, Lassen Peak's naming history is much more involved and colorful (wordful), what has been wittingly recounted by Tim I. Purdy :
Lassen Peak is the most pronounced feature in the park. In 1827 it was the venerable mountain man Jedediah Smith who first named the peak Saint Joseph's Mountain, and for years it was referred to as such. Others, not knowing Smith's name for the mountain, called it Snow Butte. The Native Americans also had their own designation for the peak. By the early 1850s it was being referred to as Lassen's Butte, for the Danish entrepreneur of the region. Some individuals, however, not knowing the correct spelling of Lassen, called it “Lawson's Butte.” Over the ensuing decades it became known as Mount Lassen, and is still commonly referred to that way. When the mountain came into national prominence during its notable eruptions of 1914-15, it prompted the United States Board of Geographic Names to resolve the name issue. On June 2, 1915, the board officially named it Lassen Peak. But not everyone embraced the official designation. For example in 1917, when the peak had another eruption, E. W. Hayden of Susanville's Lassen Advocate wrote, “Old Mount Lassen (we'll call it Mount, if we want to) had another tremendous eruption of steam, smoke and ashes on Wednesday, and the display is regarded as one of the greatest since it came back as a volcano.”
The Maidu designation for the peak is Kohm Yah-mah-nee—the phrase after which the new visitor center at Lassen Volcanic's southern park entrance is named . Here are the names for Lassen Peak again, listed roughly in chronological order of their coining: Kohm Yah-mah-nee, Saint Joseph's Mountain, Snow Butte, Lassen's Butte, Lawson's Butte, Mount Lassen, Lassen Peak.
As a prototype of the western frontiersman, Peter Lassen is not only the namesake of the southernmost volcano in the Cascade Range, but of many other geographical landmarks and regions including Lassen Emigrant Trail, Lassen County and Lassen Volcanic National Park. Lassen Volcanic includes more scenic places with an interesting naming history such as Lake Helen and Bumpass Hell.
Keywords: eponym, place name, geography, history, historic vocabulary; emigration, immigration, settling.
References and more to explore
 Franklin D. Scott: Peter Lassen: Danish Pioneer of California. Southern California Quarterly Summer 1981, 63 (2), pp. 113-136 [Preview].
 Sierra Nevada Geotourism MapGuide: Peter Lassen's Grave (No. 565 California Historical Landmark) [www.sierranevadageotourism.org/content/peter-lassens-grave-no-565-california-historical-landmark/sie7259F241EDBE1C2BF].
 Tim I. Purdy: Lassen Volcanic. Lahontan Images, Susanville, California, 2009; pp. 37-41.
 Sierra Nevada Geotourism MapGuide: Kohm Yah-mah-nee Visitor Center [www.sierranevadageotourism.org/content/kohm-yah-mah-nee-visitor-center/sie7D1F3D7A0949B69CF].