It's possible you've heard a nickname that is misunderstood or misremembered. Perhaps you've confused them with another team, or a specific instance where the term "pig" was used in a derogatory way towards their fans.
Here are some possible reasons for this misconception:
* Rivalries: Rivalries between football clubs often lead to insults and nicknames. It's possible a derogatory term was used towards Sheffield United supporters, but it never stuck as an official nickname.
* Misunderstanding: There might be a local saying or joke related to Sheffield or the club that uses the word "pig" in a way that is not intended to be offensive.
* Misremembering: It's possible you heard something incorrectly or are simply remembering a nickname from another club.
To be clear: Sheffield United does not have a nickname related to pigs. Their official nickname is The Blades, which refers to their history as cutlers and the steel industry in Sheffield.