Sweetbread

[Britney]

Either the thymus gland or the pancreas, the former
being called neck, / throat, sweetbread, the latter belly sweetbread.
The sweetbreads of ruminants, esp. of the calf, are highly esteemed as
food. See Pancreas, and Thymus.

[Ernesto]

The thymus gland (or, rarely, the pancreas) of an animal, especially as used for food.

[Monty]

the pancreas (= organ near the stomach) of a young sheep or cow, used as food