It's also used in more musical contexts, as with horns and trumpets -- for instance, "to toot one's own horn". (Animals with large trunks, like elphants and mas

It's also used in more musical contexts, as with horns and trumpets -- for instance, "to toot one's own horn". (Animals with large trunks, like elphants and mastodons, would be considered to trumpet.) The fact that a fart makes a sound like that of a trumpet merely makes it a convenient bowdlerization.