To catch a Tartar; to attack one of superior strength or abilities. This saying originated from a story of an Irish-soldier in the Imperial service, who, in a battle against the Turks, called out to his comrade that he had caught a Tartar. 'Bring him along then,' said he. 'He won't come,' answered Paddy. 'Then come along yourself,' replied his comrade. 'Arrah,' cried he, 'but he won't let me.'--A Tartar is also an adept at any feat, or game: he is quite a Tartar at cricket, or billiards.
TARTAR
Meaning of TARTAR in English
Slang English vocab. Английский сленговый словарь. 2012