Etymology

Word etymology unknown. Earliest attestation was in Song Dynasty, when the word was pronounced like *tam tik. Likely reduplicative in origin, of a type akin to Vietnamese từ láy, from an onomatopoeic root *tik meaning “to palpitate”. Compare 忒忒 (tètè < *tik tik, “to throb (abnormally)”) as well as Vietnamese thấp thỏm ~ nhấp nhỏm ‎(“uneasy, fidgety”).