1
general::
Make intense, excited, or nervous. For example, The excitement of the gallery opening has really keyed her up. This usage alludes to key in the sense of "wind up a spring-driven mechanism such as a clock." [Late 1800s]
American Heritage Idioms
2
general::
Phrase(s): key someone up
to cause someone to be anxious or excited. • The excitement of the moment really keyed me up. • Thoughts of their vacation keyed up the children so much they couldn’t sleep.
McGrawhill's American Idioms And Phrasal Verbs