“Breathe on the nostrils of a horse and it’ll be yours for life, but you have to get close. You have to earn its trust” – David, Alien: Covenant
There is a false myth about being able to tame a wild horse by just breathing on its nose, Ridley Scott used to ride horses when he was younger and believed this to be something the horses liked. Despite its inaccuracy, he liked the primal connection the android tries to forge with the Neomorph.
Most war parties were assembled to steal horses—it was easier to steal horses than to catch a wild Mustang. One of the myths that comes from white man’s stories is that Indians could blow their breath into a wild mustangs nose and tame it. This is ridiculous and untrue. Even the most skilled horse-tamers and horse whisperers cannot do this immediately. The feral wild horses were hard to catch, hard to tame and hard to keep. “Once a wild one, always a wild one.” – How Horses Transformed The Plains Indians
What does the horse mean to the Indian? Native Apache people have a deep connection to animals; they carry them through battle safely and it brings them home to their family. The Apache Indians saw it a gift from their creator.
I thought maybe the line has something to do with the Native American Indian creation myth, only two tribes have a “Flood Myth”. The most common theme in Native American Indian creation stories is the deluge. See The Mayan Creation Myth