It’s not new, but the word has been recently defined (as recent as 2012) to try and standardise and expand on existing solutions to help organisations manage their data centres more efficiently.
From Wikipedia “DCIM is new form of data center management which extends the more traditional systems and network management approaches to now include the physical and asset-level components. DCIM leverages the integration of information technology (IT) and facility management disciplines to centralize monitoring, management and intelligent capacity planning of a data center‘s critical systems. Essentially it provides a significantly more comprehensive view of ALL of the resources within the data center.”