The Rice University Neologisms Database

An unspecific exclamation that denotes either a greeting, or an expression of surprise and/or excitement Origin & Source: During Lovett’s Pirate Booty party, a group of senior boys went in costume as parrots, and every time they entered a room they would shout “perch,” as in a parrot perching on a pirate’s shoulder, until they found a seat. The word then widened semantically to become part of any loud entrance made around Lovett, as well as being adopted as a general emotional exclamation.