The term "locomotive breath" ostensibly refers to the steam ejected from a steam locomotive's pistons, which provided a characteristic foggy atmosphere and metallic odor to 19th-century train station platforms.
"Locomotive Breath" was recorded in a rather unusual manner: The entire track was pieced together from overdubs; most of the parts of the song were recorded separately. Ian Anderson did his normal flute and vocal parts in addition to bass drum, hi-hat, acoustic guitar and some electric guitar parts. Then John Evan's piano parts were recorded; Clive Bunker added the rest of the drums and Martin Barre finished the electric guitar parts. All of these recordings were then overdubbed onto each other because Anderson was finding it difficult to communicate his musical ideas about the song to the other band members.