The story
From A + DNA. Coined by Rosalind Franklin, for the first of two forms discovered during her X-ray crystallography experiments on DNA.
Etymology from Wiktionary, CC BY-SA 4.0.
A-DNA
Today it means: A configuration of DNA in cells, right-hand twisting double helix with a small size difference between major groove and minor groove, wider and more squashed twist than B-DNA; found during transcription and replication. Full definition →