They initially used the moniker national socialists, but as the party grew to power it rapidly changed gears and focused heavily on the nationalist part. Early speeches (1920s early) used the full name, whereas by the late 20s, they had pretty much exclusively switched to calling themselves nationalists in speeches.

Also, something that muddies the water but doesn't prove anything - while many socialists were arrested, socialists had an easier time adjusting to the Nazis because the Nazis hated the communists more, and socialists and communists were always at odds with each other. Socialists viewed the Nazis as a temporary partner to help deal with the communists.