The story
After Benjamin Smith Lyman (1835–1920), American mining engineer and amateur linguist.
Etymology from Wiktionary, CC BY-SA 4.0.
Lyman's law
Today it means: A linguistic rule stating that rendaku does not occur if the second element of the compound contains a voiced obstruent in any position, e.g. yama + kaji produces yamakaji (mountain fire), not *yamagaji. Full definition →