This Navajo word means: Saturday!
It’s literally “the little Sunday,” since Damóo is Navajo for Sunday.
When you think about Yázhí, and how it can mean “the little one,” keep in mind that it’s a word referring to age. For example Dibé Yázhí describes young sheep, typically lambs.
Navajo day names are entirely out of necessity of recent times. The word Damóo is likely a borrowed term from Spanish Domingo, which itself is denoting the Christian holy day.
When you consider the English weekday names – like Saturday – their roots can be references to earlier deities (like the Roman god Saturn). The fact that all Navajo weekday names are relative to “God’s day” in the Christian sense, suggests heavy influences by early missionaries – whose work on transcribing and codifying the Navajo language forms the basis of many Navajo language texts.
But just as we use Saturday without much thought about Roman religious beliefs, the true origin of Damóo remains ambiguous to many, which makes it hard to precisely trace the origins.
One way we can find out more about our sense of time is to ask more elderly Navajo people. Their grandparents were around during a time when Spanish and English were completely foreign.