What do the letters DNA stand for?

Deoxyribonucleic Acid (DNA) - National Human Genome Research Institute

Deoxyribose is a sugar with five carbons. Nucleic comes from the fact that the DNA is inside of the nucleus. Acid refers to the fact that it is a phosphoric acid.

The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T).