Inherited from Old Catalan truja, from Late Latin troia, of uncertain origin, but possibly
* from Latin (porcum de) Troia (“(hog of) Troy”), after the Trojan horse,
* or alternatively of Celtic origin, from a Gaulish root *trogja, from a root meaning “to pull” and thence also “fertile," Proto-Celtic *trāglo-, for which see Latin traho.
* or possibly simply of imitative origin, from the sound of a pig's grunt.
Compare Occitan truèja, French truie.