The detectives 'dug into' his past and learned that he had once lived in another country.
Her fingernails 'dug into' my hand. = She 'dug' her fingernails 'into' my hand.
The salesman 'dug in his heels' and refused to lower the price any further.
(..) for the old man, huh? And one priest, since you seem to know everything. Last I heard he was married to a -year-old boy, living on a beach in Thailand. Fucking family's dug into the Southie projects like ticks. Three-decker men at best. You, however, grew up... ...on the North Shore, huh? (..)2006 The Departed