At first he didn't notice it at all.
It is relatively small in contrast to her other tattoos and even then mostly obscured by her spike bracelets. But when he saw it for the first time correctly, he couldn't stop thinking about it later. A butterfly with Tony's name underneath.
She is usually not a girl for something so ... innocent. Her whole being is sometimes like a little child, but the things with which she adorn her body are often more adapted to the rest of her appearance.
He couldn't say that he understood her weakness for everything that was dark and bleak and death, but she must like it. Not him. He can't appreciate that. Not after everything he had seen in his life during his time in the Marines and NCIS.
He wanted always ask Abby if the butterfly with Tony's name has a specific meaning, but then a Petty officer was brutally stabbed with a knife and after that a little boy was kidnapped on his way home.
Every time he meant to ask her, something cropped up and in the end the image of the little butterfly disappeared from his memory. Until he saw the same tattoo a few weeks later. This time, however, it was on the wrist of his Senior Field Agent.
They had just solved the murder of a family of five and all he wanted to go home to work on his boat. Gibbs wanted to forget how the blonde hair of the little girl was so brightly highlighted against her red blood. He wanted to forget how the little boy laid in his bed hugging his stuffed dog as he (hopefully) did not feel the shot which robbed him any chance to play with it ever again. And really he wanted to forget how the unsuspecting parents lay there in the bed with their youngest child in the middle and how they would never again have the chance to cuddle with their little ones. All because someone decided that money is more valuable than the lives of five innocent people. He wanted to forget all this. He just wanted his boat and his bourbon and his basement. Everything that helped him to simply forget.
Only from the corner of his eye and almost completely absorbed in his thought, he saw how Tony stroked slowly over his artery on his left wrist. Something black briefly flashed and he tried to be as unobtrusive as possible while watching Tony as he continued to packed up his things. Tony didn't notice and continued to stroke more forcefully on his wrist ... or rather the black thing. Tony had pushed his shirt sleeve far enough up that Gibbs could finally recognize it.
A butterfly ... on the body of Anthony 'Tony' "womanizer" DiNozzo? Briefly he thought of asking Tony and Abby (he now also remembered her butterfly!) what was behind this tattoo, because it must be have a meaning. Why else would the two people have the same tattoo, who he absolutely wouldn't have something that is so absolutely sweet and fragile as butterflies.. Which brought forth the question of when Tony got the tattoo. Didn't he tell Kate that he didn't like tattoos on guys?
Just as with Abby he was distracted and he forgot all his questions.
There was a hint of a terrorist cell that was targeting a Navy ship. Any thought of his three favorite words basement, boat and bourbon disappeared. Now the only important thing was to catch these bastards and even though he felt bad about the really deserved rest for his team, he told them that their free weekend was canceled.
A few weeks passed before he again thought of the butterflies.
He did not, however, see Tony's or Abby's butterfly, but he discovered a new one on the wrist of an eye witness. As he noticed after a second glance, it seemed, however, not to be a tattoo. It looked like ... a drawing with a felt-tip pen? But why would anybody paint themself with a pen and then something like that?
But before he could continue to think about it, the young girl explained it to him. She had noticed his gaze and usually he would have kicked himself for being so conspicuous, but those thoughts quickly disappeared when he heard what a butterfly on the wrist meant .
Then he couldn't not do anything else. Whenever he had the chance, he tried to discreetly watch Tony and Abby. Tried to find clues whether the girl had told the truth.
It took a few days but there was an incident where Tony had to change his shirt and through an inconspicuous pushing up of Abby's bracelet in an embrace, he knew the truth. It hurt him that they didn't trust him enough to tell him the truth, but he understood them both. Now, however, it was time that he showed them that he was with them.
He would never have thought that he would get voluntary a tattoo, but so much was different ever since he was glommed onto by a Goth and saw the shy smile of a cop in Baltimore for the first time. Without realizing it Gibbs had found a new family and family supported each other.
That was the reason why he nearly an hour later left the tattoo shop with a small butterfly on his left wrist and as he two days later at the weekend invited Tony and Abby for dinner, watched a movie with them, let them sleep in his guest room later and wished them a good night ... there he didn't regret it.
He never regretted it for a moment when he saw Tony ogle his wrist, when the younger man carefully touched his own or when he came to him to talk to him, instead of leaving another scar on his wrist to forget the pain. Because sometimes ... sometimes someone just needs a little proof that they was not alone with their problems and even if it is only a small butterfly.