An Air Carrier crew reported MDW Ground Control commanded 'Hold Position' after the aircraft began its taxi following a taxi clearance from the alley to the runway.

Narrative

Following push from the Gate; Ground cleared us to taxi from the alley to the Runway and hold short of Yankee. I read back our clearance; to include; 'Hold short of Yankee.' As we taxied from the alley and turned right onto Tango; Ground seemed upset (as if we were not complying with instructions) and told us to hold our position. Another aircraft was taxiing on Yankee (northbound; from our left to right) and was directed by Ground to hold their position. There was no conflict; as we had planned to hold short of Yankee as directed. Ground seemed frustrated as they gave us clearance to taxi in front of the aircraft holding on Yankee short/south of Tango. We (the Captain and I) think Ground may have meant for us to hold short of Tango in the alley; but that was not the clearance they gave us; or the taxi plan we executed. With the unusual taxi instruction of; 'Hold short of Yankee'; we should have verified Ground's intentions. Ground seemed upset by our execution of their taxi instructions.