In everyday Spanish 'birria' means something worthless or a mess, a name often explained by the humble goat meat the stew was first made from.
Goat or beef is slow-braised for hours in a deep red chile and spice broth until falling apart, then served either as a stew with a bowl of consomé or shredded into tacos dipped in the fat-red broth. Market stalls in Guadalajara and rural Jalisco towns sell it especially on weekend mornings.