The following keywords are very broadly related to history.
Aksharapalli number system
Apollo space missions
astronauts
Aztec calendar
Aztec mythology
Aztec numerals: see Mayan/Aztec numerals
battles
beheaded people
Beowulf
Blue Riband
calendars
census
chaturanga
Chinese five elements
Chinese mythology
city name changes
Constitution of the U.S.
court settlements
Cuneiform numerals
Delphic maxims
disasters
Easter dates
Egyptian mythology
emperors
Epic Rap Battles of History
epithets
eponyms (words made from people's names)
etymology
expired facts
explorers
extinct animals
family tree
famous captains
famous duos
famous trips
famous women
feast days for saints
female scientists
first ladies
firsts
floods
former names
French Republican Calendar
genealogy
Google doodles
governors
Greek mythology
Hades
Hindu mythology
historical events
historical markers
"A History of the World in 100 Objects"
Hollywood Walk of Fame
House of Representatives
Hurrian mythology
The Iliad
inventions
irish mythology
Isabella Stewart Gardner Museum
Japanese mythology
Jewish sabbath laws
justices of the Supreme Court: see Supreme Court justices
John F. Kennedy
kings and queens
knights (British titles)
Latin names of cities
mass extinction events
mathematicians
Mayan/Aztec numerals
Mayan mythology
mayors
mergers and acquisitions
The MIT Blackjack Team
MIT Museum
Nautical Almanac
Isaac Newton's apple tree
Richard Nixon
non-water floods
Norse mythology
Opera Game (1858 chess game)
patron saints
people executed by hanging
philosophers
popes
postage stamps
presidential also-rans
presidents
Queen Elizabeth's corgis
revolutions
Rock & Roll Hall of Fame
Roman mythology
Secret Service codenames
Senate
six flags over Texas
space shuttle
speeches
Supreme Court cases
Supreme Court justices
treaties
UNESCO World Heritage Sites
vice presidents
world leaders