Alphabet Baby quilt by Pat

I am starting to see the usefulness of panels more.  Not that I've made any panel quilts, but I've bought tow of them! 

 This is an alphabet quilt, so A is for apple, etc.  However, I need some help on "X" and "Z"  I haven't a clue as to what they are supposed to represent, so if you know, or have a suggestion, please add it to this.

We have two suggestions for what they stand for from Michael.  "X" could be for Exercise, and "Z" for Zzz's since they appear to be going to bed.  His other suggestion is that "Z may be for Zoloft".  Anyone else want to offer up an idea?  Serious or funny, all are taken.