kick up one's heels - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Enjoy oneself, as in When she retires, she plans to kick up her heels and travel. This expression originated about 1600 with a totally different meaning, “to be killed.” The modern sense, alluding to a prancing horse or exuberant dancer, dates from about 1900.