A higher-level controlling document produces three (four including capitalization) different renditions within a page.  In LSE-62 (OCS requirements) we find:

OCS-REQ-0046 (Engineering Facility Database)

Specification: The OCS shall capture, organize and store system-wide, time tagged state information to make it available for monitoring, evaluation and calibration processes.
 
Discussion: This section will implement the requirements on the functionality and performance of the Engineering and Facility Database (EFD) as it relates to the Telescope, Camera, Data Management and Calibration operations. This includes (but is not limited to) telemetry ingestion, replication of the EFD at Base and Archive sites, support of queries and instantiation of the EFD during the development phase of the subsystems.

This telemetry and observatory condition information will be distributed to support both local and remote operations in an efficient manner.

However, in OCS-REQ-0048 (Persistence of Telemetry) we find the following descriptions of requirement parameters (rearranged a bit for clarity):

• Blob_AvgRate: Long-term mean ingest rate to the Engineering and Facilities Database of non-science images required to be supported.
• EFD_AvgRate: Long-term mean ingest rate to the Engineering and Facilities Database required to be supported.
• EFD_DayStore: The minimum supported daily data volume of the engineering facility data base.
• NonScience_MaxRate: Maximum ingest rate to the Engineering and Facilities Database of non-science images required to be supported.

I'm fine with standardizing on the singular, with the "and".

Hah, LSE-72 (DM-to-OCS ICD):

It very consistently says Engineering and Facilities Database, except that in its glossary it has Engineering Field Database (?!?).

lsst-texmf update on PR#194.

Not claiming any bonus points, in the interests of simply getting this done and moving on.