The word daṇḍa means rod or pole. A rod or pole falls straight; similarly, when one offers obeisances to his superior with all eight aṅgas (parts) of the body, he performs what is called daṇḍavat. Sometimes we only speak of daṇḍavats but actually do not fall down. In any case, daṇḍavat means falling down like a rod before one’s superior.
Ref >> Srila Prabhupada Vani.