einen Zahn zulegen
to speed up; to get a move on
Origin
Origin not entirely certain: an older reading points to the medieval hearth, where the pot was hung one 'tooth' lower on the notched kettle-hook to raise the heat; more likely, though, the phrase refers to the toothed ratchet of the hand-throttle in early motor vehicles (first half of the 20th c.).
Building blocks
Words in this expression
Examples
Wenn wir den noch , wir einen .
If we still want to catch the train, we'd better get a move on.