I can’t remember ever seeing hoarse used when the writer actually meant horse (e.g. “I’m going to turn out my hoarse”) but it does seem common the other way round (e.g. “sorry, I’ve gone a bit horse”). That’s all the excuse I need to write a post that enables me to use a magnificent image of a magnificent animal.
Hoarse
- (of a voice) rough, harsh and/or unclear
- having a rough, harsh and/or unclear voice

Horse
- a solid-hoofed, four-legged domesticated mammal with a mane and tail
- a frame or structure used to support or mount something or someone
- to provide someone or something with a horse (or horses)
My tip: hoarse is often harsh.
Sources:
Proot is a word said to donkeys (or mules) to encourage them to move faster. Its origin is unknown. It could be related to the word proo, which is used to call cows and command horses. My understanding is that proo is imitative of a sound the animals naturally respond to.
You might be most familiar with these homophones as a brand of footwear (Dr. Martens) and a common male name (Martin). But if you find yourself writing or reading about wildlife, it is important to know the difference in that context.