Learn English – Medieval term for sister and brother in-law

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Is there a medieval term for sister/brother-in-law? The only example I could find was in GRR Martin's A Song of Ice and Fire series where he uses the terms goodsister and goodbrother. Are those rooted in actual medieval terms for in-laws? Were the in-laws even addressed as members of family with specific words? (I've read somewhere that before 19th century the in-laws were used instead of step-mother/father/etc., so they could not be used for the other relation or would be very confusing).

Best Answer

According to the Oxford English Dictionary, they have been called in laws for a while. Here are its earliest examples of each:


Later, in the 1530 Tyndale Bible (a little too late for it to be considered medieval) shortened versions of these terms, sister law and brother law, were used (again, the earliest examples I could find in the OED):

Yf the man will not take his systerlawe, then let her goo to the gate vnto the elders and saye: My brotherlawe..will not marie me.


Confusingly enough, sometimes they are simply referred to as brother and sister according to the OED:


In addition, good brother and good sister were used, but mainly in Scottish English. The OED's earliest respective citations are:

  • Iames steward, that ledar was Eftir his gud brother disses.
    The Bruce, 1375

  • That his gud systyr the Quenys grace be nocht therby mynyst in hyr autorite.
    Douglas Book, 1515

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