Extensive research has revealed to me that the old people are kicking "eunhaeng" trees. That happens to be the word for bank (the faltering sort, not the aquatic one), but in this case it means GINKGO BILOBA! I know that word from pharmacies and healthfood stores. Apparently doctors here tell old folks to eat somewhere between 5 and 20 ginkgo nuts a day, and they can be a little expensive, so people beat on the trees.
Unfortunately, it's illegal. I think maybe I'll go tell the police to do a little 6AM stakeout. That's what old people get for expecting me to insert honorifics and humilifics into my speech.