1. Also, keep up with. Proceed at the same pace, continue alongside another, as in We try to keep up with the times. [First half of 1600s] This usage, also put as keep pace, appears in the phrase keeping up with the Joneses, which was coined in 1913 by cartoonist Arthur R. Momand for the title of a series in the New York Globe. It means "trying to match the lifestyle of one's more affluent neighbors or acquaintances." For example, Their buying a new van is just another attempt to keep up with the Joneses.
2. Support, sustain, as in They're trying to keep up their spirits while they wait for news of the crash. [Late 1600s] Also see keep one's chin up.
3. Maintain in good condition, as in Joan really kept up the property. [Mid-1500s] This usage also appears in the idiom keep up appearances, meaning "to maintain a good front, make things look good even if they're not," as in She was devastated by his bad prognosis but is trying hard to keep up appearances for their children. [Mid-1700s]
4. Persevere, carry on, prolong, as in Keep up the good work, or How long will this noise keep up? [Early 1500s] Also see keep it up.
5. Also, keep up with; keep up on. Stay in touch, remain informed. For example, Ann and I haven't seen each other since college, but we keep up through our annual Christmas letters, or We subscribe to three papers so as to keep up on current events. [c. 1900]
6. keep someone up. Cause someone to remain out of bed, as in He's keeping up the children beyond their bedtime. [Mid-1700s]