Maria Hill: What does S.H.I.E.L.D. Stand for, Agent Ward?
Grant Ward: Strategic Homeland Intervention, Enforcement and Logistics Division.
Maria Hill: And what does that mean to you?
Grant Ward: It means someone really wanted our initials to spell out "shield."
The call sign for the mobile command center is SHIELD 616. Earth-616 is the name for the primary universe in Marvel comics.