Where does “grandmother-in-law” come from?

grandmother-in-law (English) comes from English in-law, from English -in-law, from English mother-in-law, from Middle English moder in lawe — mother-in-law.

grandmother-in-law (English): A grandmother of one's spouse

Definitions

  1. A grandmother of one's spouse

Ancestry of “grandmother-in-law”, step by step

grandmother-in-law traces back through two separate lines of ancestry.

via English in-law

StepLanguageWordMeaning
1Englishin-lawA relative by marriage (or through affinity)
2English-in-lawRelated through marriage
3Englishmother-in-lawThe mother of one's spouse; A mother-in-law...
4Middle Englishmoder in lawemother-in-law

via English grandmother

StepLanguageWordMeaning
1EnglishgrandmotherA mother of someone's parent; A female ancestor...
2Middle Englishgraundmodre
Every word from Middle English moder in laweEvery word from English -in-lawEvery word from English in-law