The story
The earliest known use is from 1889. Possibly a fanciful coinage, from snicker + doodle (“doodlebug”; though without clear semantic connection to either word). An alternative etymology derives it from (Palatinate) German Schneckennudel, Scheckennurel, Schleckenuʳʳl (with variants in other dialects, such as in Swabia and Saarland), also a round type of pastry, but formed from dough rolled up in a coil. However, these words do not appear to have surfaced in 19th-century American English, and early attestations of snickerdoodle do not suggest a German-American connection. A Dutch origin has also been surmised, based off semantics (see cookie) and similar-sounding words (see snickersnee).
Etymology from Wiktionary, CC BY-SA 4.0.