It's here: Shiwasu (師走, the month of December), whose kanji characters are composed of shi (師, teacher) and hashiru (走る, running) — put them together and you get a month so busy and jam-packed with events that even teachers have to sprint to get everything done.
The term goes back several centuries, and though teachers are now busy all year round along with the rest of us, December remains especially tight, hectic and ochitsukanai (落ち着かない, unsettled). What with deadlines for everything coming down to the wire along with colds, flu and stomach pains (from the numerous drinking parties scheduled throughout the month) that assail us every few days, Shiwasu can be a real pain in the lower extremities.
When I was growing up, the closer it got to nenmatsu (年末, end of the year) the more stressed out and ira-ira (イライラ, irritated) the adults became, to the point that any family member found lolling in front of the TV in that most deplorable of states: te ga orusu (手がお留守, hands still and doing nothing), was to be dragged before my grandmother and given a full lecture.