My son saying the "N" word

Ok, my son is not really using that "n" word, at least not intentionally.  There is a dog in my husband's family that is named "Negra."  My hubbie is Hispanic and his entire family is mostly Spanish speaking.  The dog is black and "negra" in Spanish means black.  I don't know if anyone names their pet whitey, or blacky, or yellowy, etc. but it just doesn't sound right especially when my 3 year old calls its name.  You can imagine a sweet little boy chasing a little doggie going "Come here, Negra!  Negra, Negra, Negra!"  It doesn't sound like it is suppose to.  Every time we are outside or at an event where they take the dog, I cringe when he calls that dog's name.  I am just waiting for an outsider to give me a dirty look or  come up to me and slap me in the face for allowing my son to use that kind of word.  So far, no one has done either but I don't really look around to see if anyone is giving me that "look."  Since we live in an area that is mostly Hispanic, that might be the reason we don't get the dirty looks because someone  might hear my little boy and at first think as Dave Chappelle puts it "oh my God, that is racist," but then look at him chasing a black dog and then think, "Oh, he is saying Negra which is black, whew!"  I am not Hispanic and did not grow up with hearing dogs being called blacky or "Negra" so I just can't fathom calling a pet those names since it doesn't sound right.  What happened to the cute names like Spot or Fluffy?  Those don't sound questionable do they?  I'm sure even those names could be turned around and offend someone out there too.  Maybe someone who has a skin condition might not  like Spot or Fluffy might offend a person going bald, but c'mon, "Negra," that sounds like the stomach turning "N" word when you hear it from a preschooler.  This reminds me of the time I was in kindergarten.  School was over for the day and I started running and skipping down the big hill that is outside the elementary school.  My dad was at the bottom of the hill waiting for me with a big grin on his face as he was looking at his precious little girl happily singing a song that I had heard so many times before.  It goes a little something like this.... "Went to the river and I couldn't get across, jumped on a N***er cuz I thought it was a hoss,"  I'm sure there were other disgusting words to that song that I can't seem to remember because from that day, I think my Dad removed them from my brain.  My dad's big grin turned into an expression of "Oh my God, what the hell are you singing and why are you singing it in front of all these other parents who are going to look at me and beat me down?"  My dad looked at me with sweat pouring down his face and asked "Where did you hear that song!!?" and I replied "Papa."  That is what I called my grandpa(my mom's dad, but I'm sure my dad's dad was equally racist-just didn't sing songs to me) My dad says "Well I'm going to have a talk with Papa, you are to never sing that song again."  Then I'm sure he explained to me why.  My Dad always taught me to treat everyone the same and to never think that I was better then anyone because I was white.  There were other lessons too about race and other things, but my point is I was not raised to think or say these types of things.  So now as an adult, hearing my son shout out a derogatory word like that immediately sends shivers down my spine.  Plus, what doesn't help is when he says the dog's name, there are other people around that laugh and think it is funny.  Ok, so I know it isn't just me and I am not being sensitive about it, he really does make the word sound not the way it was intended.  I mean, for pete's sake (never thought I would use that phrase in my life), can't they just call the dog, "Doggie?"  That is what you call the dog anyway, "Here doggie doggie."