sororicide
noun
so·ror·i·cide
səˈrȯrəˌsīd
plural -s
1
: the act of killing one's sister
2
: a person who kills his sister
Word History
Etymology
in sense 1, from Medieval Latin sororicidium, from Latin soror sister + -i- + -cidium -cide (killing); in sense 2, from Latin sororicida, from soror + -i- + -cida -cide (killer)