What is the significance of Chewie's white patch?

Question

In the novel Crystal Star by Vonda McIntyre, Leia and Chewbacca stumble upon a fleet of Imperial slave ships. At that moment, the following exchange occurs:

Chewbacca touched the thick chestnut fur at his throat. He raised his chin, combed his fingers through his pelt, and revealed a patch of stark white hair. He let her look at it for a moment, then lowered his head again.

"Is that--?"

He growled in assent.

Chewbacca had been a slave. Not a colonist-slave, but the chattel of an Imperial officer. Leia knew very little about that part of his life. She knew he had been kidnapped from the deep and magical forests of his world. He had been chained, and punished for any defiance, and worked nearly to death.

This patch of stark white hair isn't mentioned again, and no further connection is made between it and slavery. I thought maybe the fur was white under where his collar sat, but that doesn't seem to be the case, as the fur wouldn't be deep under the pelt, nor just a patch.

What is the significance of this "stark white hair", and why does it lead Leia to think about Chewie's past as a slave?

Answer 1

A freeze brand, signifying Chewbacca's enslavement.

Chewbacca's white patch resembles a freeze brand, such as this closeup of one on a brown-furred animal:

(Caution: This image is not gory, but some people might find it disturbing.)

— Wikipedia: File:LeftShoulderBrand.JPG

Freeze branding causes less damage than hot branding:

Freeze branding is a branding process that involves the use of liquid nitrogen or dry ice and alcohol to cool a branding iron so that the iron may then be used to alter the hair follicle of an animal to remove the pigmentation or to remove the hair altogether, depending on the color of the animal. Hair in the branded area will grow back white. On animals with white hair or no hair, the iron is left on the skin long enough so that the hair falls out and the area is balded or the skin depigmented. It is most commonly used as an identification mark for ownership.

Freeze branding is used as an alternative to the more traditional hot branding. This process involves the use of a hot iron to scar an animal's skin, which can be painful and traumatizing to the animal ... There has been debate whether freeze branding truly is less painful than hot branding, but studies conducted to compare the pain of the two methods have concluded that freeze branding is indeed less painful.

— Wikipedia: Freeze brand (emphasis added)

The Imperials who chose freeze branding over hot branding were likely concerned less with Chewbacca's comfort than with minimizing the chance of infection which could lead to lost productivity:

Since the skin is not broken and there is little or no pain, freeze branding is only mildly stressful to the horse, and unlike hot-iron branding, there is no risk of infection, since there is no burn or harm to the underlying skin. Only the hair follicle is affected.

— Horse identification

Answer 2

According to Wookieepedia, their life expectancy is 400 years, and Chewie is "only" around 230 years old. So Leia may just be surprised he's got a grey streak already, and his past as a slave would undoubtedly have contributed to that.

Maybe related, there's the story of Chewie and [Hronk] (https://starwars.fandom.com/wiki/Hronk):

As they were pulled aboard, Chewbacca quickly came up with a plan to hide their new passenger, who had just come to his senses. He had Hronk cover the white streak in his fur with grease so that he looked indistinguishable from Chewbacca to Quirt and his men, who could not tell Wookiees apart.