1
general::
When a situation is urgent or desperate, as in When the chips were down, all the children came home to help their mother. This expression comes from poker, where chips represent money being bet. When all the bets have been made, and the chips put down, the hand is over and the players turn up their cards to see who has won. [Late 1800s]
American Heritage Idioms
2
general::
Phrase(s): when the chips are down
Fig. at the final, critical moment; when things really get difficult. • When the chips are down, I know that I can depend on Jean to help out. • I knew you would come and help when the chips were down.
McGrawhill's American Idioms And Phrasal Verbs