1
general::
Phrase(s): throw someone or something in
Go to throw someone or something into something., Phrase(s): throw something in
Go to throw something into the bargain.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
1. Insert or introduce into the course of something, interject, as in He always threw in a few jokes to lighten the atmosphere. [c. 1700] 2. Add something with no additional charge, as in The salesman said he'd throw in the carpet padding. [Second half of 1600s] 3. throw in with. Enter into association with, as in His friends warned him against throwing in with the notorious street gang. [Second half of 1800s] Also see CAST ONE'S LOT and the subsequent idioms beginning with THROW IN.
American Heritage Idioms