$FG,2$$WW,1$AutoComplete$FG$ is the $FG,7$LTGRAY$FG$ window on the right of the screen. $LK,"ACInit",A="MN:ACInit"$() collects words from all text files in subdirectories. Normally, the call to $LK,"ACInit",A="MN:ACInit"$() is in $LK,"HomeSys.CC",A="FF:~/HomeSys.CC,ACInit"$. It provides auto-complete for typing, jump-to-code and jump-to-dictionary functionality.
If you have the raw Project Gutenberg dictionary file, you can generate the ZenithOS processed dictionary files with the stand-alone program $LK,"::/Zenith/AutoComplete/ACDictGen.CC"$.