Green’s Dictionary of Slang

choop adv.

(Anglo-Ind.) quietly.

[UK]Kipling ‘The Three Musketeers’ in Plain Tales from the Hills (1889) 71: ‘Thin chel. Shaitan ke marfik, an’ the chooper you choops an’ the jildier you chels the better kooshy will that Sahib be; an’ here’s a rupee for ye?’.