What word or phrase does your mother always say?
c.1300, "wicked, evil," from shrewe "wicked man" (see shrew). Cf. crabbed from crab (n.), dogged from dog (n.), wicked from witch (n.). The sense of "cunning" is first recorded 1510s. Related: Shrewdly; shrewdness. Strutt's "Sports and Pastimes of the People of England" (1801) has a shrewdness of apes for a company or group of them. Shrewdie "cunning person" is from 1916.