To understand the raw nerve this concept hits, one must travel back in time. The term "slave" is not a light metaphor. In the United States and the Caribbean, chattel slavery (1619–1865) involved the legal ownership of human beings. Branding and tattoos have a dark history here—enslavers sometimes tattooed or branded identification marks on the chest or shoulders of the enslaved.
Here is a comprehensive guide to the meanings, cultural contexts, design variations, and placements of the slave butterfly tattoo. The Core Symbolism: Pain Meets Liberation slave butterfly tattoo