Slughorn can refer to several things and one (fictional) person.
It is an obsolete form of the word slogan, closer to its derivation from the Scottish Gaelic sluagh-ghairm (meaning war-cry).
In turn this influenced the pseudo-Medieval poetry of Thomas Chatterton. For example, in a poem about the Battle of Hastings he writes "some caught a slughorne and an onsett wounde" (Battle of Hastings ii.99), meaning "some picked up a slughorn and sounded a charge". A slughorn in this context appears to be some kind of trumpet. However, in a footnote to another usage of the word, Chatterton defines it as "not unlike a hautboy". The Medieval English word hautboy is the origin of the modern word oboe and has never referred to any instrument comparable to a trumpet.
Chatterton's usage inspired Robert Browning in his poem Childe Roland to the Dark Tower Came, in particular the last stanza in which the hero sees the ghosts of all those who died trying to reach the Dark Tower before him.
Horace Slughorn is a character in the Harry Potter series of novels by J. K. Rowling.
Slughorn is the name of openSUSE's mascot for the YaST2 setup and configuration program.
The Discworld novel Guards! Guards!, in a reference to Chatterton and Browning, has the false king sound a slughorn to challenge the dragon, described as "like a tocsin, only deeper" and prompting one character to comment "It must have been a bloody big slug".
