Sweetbrad or Sweetbread: How To spell?

The word Sweetbrad is misspelled against Sweetbread, a noun meaning "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."