As part of the Navajo introduction and clanship system, this word references your father’s first clan. Since every Navajo is their mother’s clan (meaning her’s is the “first clan” or the one her children pass on to their children), their father’s clan is the one they would be “born for”.
For example: Hashk’aan hadzohí báshíshchíín (I am born for Yucca-fruit-strung-out-on-a-line)*.
This essentially means the second clan is the father’s mother’s (mother’s mother’s …) clan.
The Navajo figure Tó bájíshchíní, who was one of the mythical warrior twins that vanquished giant monsters, is named “Born for water”, or “child born of water”.
In the third person, this word becomes yáshchíín (he/she is born for). This way of recognizing oneself or another helps to structure relations among Navajo people, and can sometimes lead to scrutiny if partners are related by clanship. Strictly speaking, it is not totally disallowed for two clan relatives to be engaged if the elders are confident that there is no immediate or blood relation. This takes a convening of families and extensive comparison of their family trees.
Another word referencing the father is shitaa’ – but that is more referring to a spiritual father (father sky).
*Cultural note: hashk’aan is also a word for banana, so I could be given the nickname Banana Boy and teased (not harshly).