Definition & Meaning of "[work] like a (horse|dog|Trojan)"

What is the origin of the idiom "work like a horse" and when to use it?

The phrase "work like a horse" is believed to have originated in the 17th century, and it is a reference to the hard work and endurance of horses, which were commonly used as draft animals during that time. It is used to describe someone who works very hard, often for long hours and with great dedication. It can be used in both personal and professional contexts.