[embit]

In India, mutton is older goat not a sheep. So word mutton means older sheep or goat depending on which country one is taking about.

[hackernewds]

Mutton always means goat. However, lamb is often substituted for mutton.

[pleb_nz]

Mutton in NZ and Oz is older sheep, hoggart is sheep between lamb and mutton in age and lamb is well, the youngest and called lamb.

https://www.handsourced.com.au/behind-the-scenes/whats-diffe...