I bet a little just got trapped under the tonge and then caught hold of more, causing it to build up. The movement of the tongue probably kept moving it down and slowly made the lump.
I will ask my waterfowl friends this weekend as I'm not so wise with Geese :roll:
I know long grass at this time of year with chickens can cause an impacted crop / a blockage in the crop- the sort I'm talking about isn't green lush lawn type of grass but the meadow type that has gone to seed, turned brown and is harder to break.
I'm glad you found it and sorry you got pecked!