"Sierra, hotel, india, echo, lima, delta" are all code words that are a part of NATO's phonetic alphabet. Sierra is the code word for the letter "s". Hotel is the code word for the letter "h". India is the code word for the letter "I". Echo is the code word for the letter "E". Lima is the code word for the letter "L". Delta is the code word for letter "d". "Shield" is what the code means.