Allgemeine Theorie der Beschäftigung, des Zinses und des Geldes
Today these ideas, regardless of provenance, are grouped in academia under the rubric of "Keynesian economics", due to Keynes's role in consolidating, elaborating, and popularizing them. Keynes himself specifically discussed underconsumption (which he wrote "under-consumption") in "The General Theory of Employment, Interest and Money".