[Twee.dle.dum and Twee.dle.dee] n [E tweedle to chirp + dum (imit. of a low musical note) & dee (imit. of a high musical note)] (1725): two individuals or groups that are practically indistinguishable
TWEEDLEDUM AND TWEEDLEDEE
Meaning of TWEEDLEDUM AND TWEEDLEDEE in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012