The Spanish word 'morcilla' (meaning blood sausage) comes from Medieval Latin 'morsella', meaning 'small morsel'. This Medieval Latin term was derived from the Classical Latin word 'morsum', which meant 'bite' or 'morsel'. The evolution from a general term for a small bite of food to specifically meaning blood sausage reflects how this type of sausage was traditionally served and eaten in small portions.

A related Spanish word is 'mordisco' (meaning 'bite' or 'nibble'), which also comes from the same Latin root 'morsum'. While 'morcilla' evolved to specifically refer to blood sausage, 'mordisco' retained the more general meaning of taking a bite of something.

The English word 'morsel' is a cousin of 'morcilla', as it also derives from Latin 'morsum'. While 'morcilla' specialized to mean a specific type of sausage in Spanish, 'morsel' kept its original meaning of a small bite or piece of food in English. The English word 'morselize' (to break into small pieces) is another related term from the same Latin root.