shooing with a gum

How does one introduce a child to "forbidden/taboo" notions. I am not talking about sex education here. We still have some way to go before we get there.
Our 4 yr old gets very little TV time and whatever precious little he gets to watch is typically kiddy, animation stuff - main-stream TV is completely off the hook since we do not watch any TV/videos/movies when he is around. He is not into action figures or anything like that either. Of late though, we hear words from him such as "I will shoo you with a gum". It took as a while before we mapped this to "I will shoot you with a gun". We are guessing he got this from his school friends (who may have elder siblings around). Now, I am not sure what he understands about gun/what happens when someone shoots with it etc..I am not entirely sure how to explain this to him either. While I would want to shield him from such talks for as long as I can, I also don't want him to be ignorant of these concepts and worse learn about these things from his friends for the first time. Would love to know how my readers would talk about these (gun, swords, violence in general) to a active,still-innocent, over-imaginative kid in a healthy manner. 

Many a time, I have come to this space to pen down my thoughts but return blank.
I have observed that typically my thoughts flow uninhibited into words here when what I have to share is something of a negative nature. Maybe because inherently I believe in the "nazar lag jayegi" / "temping fate" concept if I were to share happy thoughts.

Anyways, nothing specific to share today just wanted to write something - so random stuff it is.

Work has been decent for the last couple of months but just about rising from the trough, so expect things will be hot sometime soon :(. M has been perpetually busy with work so haven't been able to go on a outing since June. I know he wont like this comment if he happens to read this but that is the truth. We are planning for a weekend outing to Mendocino coast next weekend but lets see how things work out. Travel bug is biting hard - gotta do something abt it.

Summer this year has been a bliss. M's parents are here with us and Naman's been having a ball of a time with them. It has been nothing but pure joy to watch him bond with them. Be it reading to him or playing "teacher teacher", "pappa/mumma/baby", "fire-fighter" /any other make believe games he comes up with, they are always enthusiastic to be a part of his schemes and they are such fantastic sports too! They are ever willing and patient to answer the gazillion questions he throws at them. Truly, Naman is blessed to have them in his life and so are we. Indeed, every time I spend time with this amazing couple, I glean enough things to fill pages.

Naman continues to be the joy of our lives. He has started taking piano lessons this summer. His teacher tells me that he is doing quite good for his age. He certainly shows interest and great deal of aptitude. He can play "old MacDonald" to perfection and some other music by looking at notes. Music practice sessions at home continue to be a power struggle and inevitably end with him composing a "Let's go to the temple" song with so much seriousness - it has all of us bursting into laughter. This "temple/God loving" trait has come about recently. He even allots a "prayer room for ganapati Jai-Jai chami" in all of his drawings - which typically is a multi-tasking vehicle - something on the lines of  "double-decker fire-truck/ambulance/rocket ship". This vehicle switches from one mode to another at the click of a button. Even his ambitions are on the same lines. If you ask him what he wants to be, his answer these days is "fire-fighter,astronaut, ambulance-driver, construction uncle". Oh, all in all he regales us with his tales and jokes and his teachers at school say that he is a non stop entertainer at school as well. So there, my son is all set to be a joker :D