Voilà :
-bash-3.2# diskutil eraseDisk jhfs+ BOOT disk0s5
A volume was specified instead of a whole disk: disk0s5
Specify a whole disk, or instead use diskutil eraseVolume to erase a volume on a specific partition
-bash-3.2# diskutil eraseVolume jhfs+ BOOT disk0s5
Started erase on disk0s5 OS X...