Where does “alternating case” come from?

alternating case (English) comes from English alternating, from English alternate, from Latin alternātus, from Latin alternō, from Latin alternus, from Latin alter, from Proto-Indo-European h₂élteros, from Proto-Indo-European h₂el- — to grow, nourish; beyond, other; to wander, roam.

Ancestry of “alternating case”, step by step

alternating case traces back through two separate lines of ancestry.

via English alternating

StepLanguageWordMeaning
1Englishalternatingpresent participle of alternate; That alternates;...
2EnglishalternateHappening by turns; one following the other in...
3Latinalternātusalternated, vacillated
4Latinalternōto do one thing and then another, do by turns, interchange, alternate
5Latinalternusalternate (one after the other), successive
6Latinalterthe other, the second; the one...the other
7Proto-Indo-Europeanh₂élterosother , second
8Proto-Indo-Europeanh₂el-to grow, nourish; beyond, other; to wander, roam

via English letter case

StepLanguageWordMeaning
1Englishletter caseThe distinction between majuscule (uppercase) and minuscule (lowercase) letters
Every word from Proto-Indo-European h₂el-
alternating case — Etymology, Origin & Word History | Etymology Explorer