A language usage nitpick that's been bothering me. In 16th/17th century documents, I've seen the word "sister" refer to a spouse's sister or a brother's wife, what we would now call a "sister-in-law". I've also seen "son-in-law" used to mean a stepson. Does anyone know when the modern meaning of "in-law" became standardized? Would it seem anachronistic to use "sister-in-law" in the 17th century? Should I just say "sister" or "husband's sister"? Am I overthinking this?