A burro is a small donkey. Burrow means (1) a hole or tunnel, or (2) to dig a hole or tunnel. A third homophone is borough (sometimes shortened to boro in the U.S.), which is primarily a noun referring to administrative divisions within some towns, cities, and states.
The words are homophones or nearly homophones in most parts of the English-speaking world, but they are otherwise unrelated. Burro, which is used primarily in the Western U.S., came to English from Spanish, where it is short for borrico, a word for donkey with Latin origins.1 Burrow‘s origins are more mysterious, but it likely has Germanic origins.2 Borough comes from the Middle English burgh, for city, which itself has roots in Old English.3
Wild horses and burros are descendants of animals released by or escaped from Spanish explorers, ranchers, miners, U.S. Cavalry, or Native Americans. [KY Post]
They’ve emerged from their burrows, hungry and on the hunt for females to satisfy their insatiable desire to mate as much as possible. [Herald Sun]
The Nets bask in being in a borough that seems to grow more vibrant by the day. [New York Times]
There are currently over 50 thousand horses and burros in holding facilities, while the numbers running free are in question. [Kern Valley Sun]
That practice forces roots into a competitive battle so that they burrow deep into the underlying silt for vital resources. [Globe and Mail]