Osmo is a Finnish masculine given name, meaning "island" or "frozen sea". It's often associated with the Finnish composer Jean Sibelius, who had an older brother named Osmo. The name has gained some popularity outside Finland, particularly in Sweden and Norway.
"Osmo saw an increase in its popularity as a baby name between 1915 and 1917, with a total of 13 babies being named Osmo during these two years."