Yichus (יִחוּס‎ yḥws), a Hebrew-based Yiddish word meaning "lineage". In some past and present Jewish communities, good yichus—meaning descent from a family of high reputation—is necessary for a person to be considered as a potential marriage partner. Colloquially, the term refers to the chain of origin for a statement, creative work or object.^[1]

Yichus first appeared in the Hebrew Bible in the Book of Ezra.^[2] It appears in Ezra 2:62 and Nehemiah 7:5), where the Hebrew root (yud-chet-sin) means "relation to" or "related to."^[2] In the later rabbinic Hebrew, the last letter of the root changed from sin (ש‎) to samekh (ס‎), though the pronunciation and meaning remained unchanged. The latter spelling (yud-hey-samech) appears frequently in rabbinic literature.^[3]

Although the word yichus originated in Hebrew,^[4][5] the term is generally accepted as a Yiddish word that has flowed into modern English. The anglicized word has been transliterated as yichus,^[6] yikhes,^[7][8] yiches,^[9] and yikhus.^[10]

As far back as the Talmudic era, being son-in-law to someone widely respected was valued.^[11] Subsequently, even the yichus of being son-in-law to the son-in-law and similar lineage links were valued. From the 14th century onwards, yichus was an important concern for Eastern European Jews.^[7] Good yichus could refer to Torah scholarship or wealth, while bad yichus resulted from the suspicion of illegitimate descent.^[7] However, many rabbis disapproved of the concept of yichus, instead insisting on judging individuals based on their personal merits.^[2] "In Lithuania some Jewish families hid their Yikhus (lineage)".^[12] There was a tension between yichus on one hand, and "meritocratic leadership based on scholarship" on the other.^[7] Judgments of yichus became one of the mechanisms which determined social hierarchies.^[7] From the 19th century, the significance of yichus declined as more marriages were based on romantic love,^[13] and reformers criticized yichus for leading to inbreeding within small circles of "acceptable" families.^[7] However, nowadays yichus is still an important qualification for marriage in charedi communities.^[14][15]

The family trees, or pedigree charts, of Jewish families, listing genealogy and family history records, have been identified with several names, among which are yichus book,^[16][17][18] yichus brief,^[19] and yichus record.^[20][21] To help a child trace lineage, some families would write a "yichus book".^[22] The focus of a yichus brief (letter of relationship)^[23] is not as extensive as a yichus book^[24][23][25] whereas a yichus book or yichus record/"sefer yuchsin"/registry^[20] is community-oriented. Some families also kept a separate "Register of Circumcisions".^[22]

Being the mechutan (מְחוּתָּן, father of one's child's spouse^[26]) of a notable person is sometimes considered important enough to include in a wedding invitation and in giving other credentials.^[27][28] Although primarily used for same generation relatives, it can be used beyond that generation.^[29] Being a ben achar ben (literally son-after-son, i.e. patrilineal) descendant is sometimes considered more notable than other forms of descent.^{[30][31][32][33]}

For various reasons, surnames/family names were changed, and sometimes reverted.^[22] Thus, Jewish family names have not always been a reliable indicator of ancestry. For example: certain family names, such as Cohen, are not as strongly indicative of being a Kohen as Katz.

• Dem Ganefs Yiches (The Thief's Lineage), a 19th century song parodying the concept of yichus