When we got engaged, my wife and I asked our parents what they wanted to be called by their child-in-law. My parents preferred “Shver” & “Shvigger” and my FIL & MIL preferred “Totty” or “Ta” & “Mommy” or “Ma”. We have both gone along with their requests though it was sort of uncomfortable for both of us at first. It has been many years since, but as we learned, one can get used to anything, and we are happy to call them what they prefer.
BTW, my parents, recognizing that “Shver” & “Shvigger” are unusual names to call one’s FIL & MIL nowadays have NEVER INSISTED that any of their children-in-law call them those. They always mention these names to each of their CILs when asked but go along with “Totty” or “Ta” & “Mommy” or “Ma” when they see that any child-in-law is too uncomfortable with “Shver” & “Shvigger”. Therefore, as of now, 2 of their CIL call them “Shver” & “Shvigger” while the rest call them “Totty” or “Ta” & “Mommy” or “Ma”.
AFA my parents vis-a-vis their own in-laws, my mother has never had a MIL but she called my father’s father “Abba” — just as he (and all the other children-in-law) did. My father calls my mother’s parents “Shver” & “Shvigger’ per their request (which is why I always considered this practice to be “normal” and was uncomfortable at first calling my in-laws “Totty” or “Ta” & “Mommy” or “Ma”).