"Russian radical socialist of the revolutionary period," 1917, from Russian bol'shevik (plural bol'sheviki), from bol'shiy "greater," comparative of adjective bol'shoy "big, great" (as in Bolshoi Ballet), from Old Church Slavonic boljiji "larger," from PIE root *bel- "strong" (source also of Sanskrit balam "strength, force," Greek beltion "better," Phrygian balaios "big, fast," Old Irish odbal "strong," Welsh balch "proud;" Middle Dutch, Low German, Frisian pal "strong, firm").
The faction of the Russian Social Democratic Worker's Party after a split in 1903 that was either "larger" or "more extreme" (or both) than the Mensheviks (from Russian men'shij "less"); after they seized power in 1917, the name was applied generally in English to Russian communists, then also to anyone opposed to an existing order or social system. Bolshevism is recorded from 1917.
"native or inhabitant of Denmark," early 14c. (in plural, Danes), from Danish Daner, (Medieval Latin Dani), which is perhaps ultimately from a source related to Old High German tanar "sand bank," in reference to their homeland, or from Proto-Germanic *den- "low ground," for the same reason.
It replaced Old English Dene (plural), which was used of Northmen generally. Shakespeare has Dansker "a Dane" (c. 1600). Dane was applied by 1774 to a breed of large dogs.
Danegeld (attested from 1086; it was first imposed in 991) supposedly originally was a tax to pay for protection from the Northmen (either to outfit defensive armies or to buy peace), continued under later kings for other purposes. Danelaw (c. 1050) was "the body of Danish law in force over that large part of England under Viking rule after Alfred's treaty in 878;" the application to the land itself is modern (1837, Danelagh).