Icebergs like C19A are named I believe in part to their coordinates on a map.
With an approximate size of 2,264 square miles in size, C19A became the largest iceberg in the world after the previous largest iceberg, B15 broke into two different pieces. The B15 weighed in at around 4,400 square miles in size. As the B15 iceberg continues to break up, the C19A takes the title of largest 'berg until it starts to cracks.
A giant crack across the B15 iceberg broke it off into two pieces in the last month.