Do you want to go for L-U-N-C-H and maybe a W-A-L-K?
Dogs often learn the word "walk" and get excited if someone says it: so humans disguise the word by spelling it out so they don't recognize it and they don't feel guilty for not taking them on a walk in the moment. Here, the humans want to go to lunch separate from their co-worker dogs, so are spelling out the word lunch to not invite them.