His tattoo reads "MOTHER LOVE", which is also the name of a song द्वारा Queen. It's progably a reference to the band as they've done it before with Claire in Code Veronica. (She wore a जैकेट with the words "Let me Live" on the back; another song द्वारा queen.)
But getting back to Billy~ Personally, I think the lyrics in the song MOTHER प्यार can relate to him.
