Where does “shall've” come from?

shall've (English) comes from English shall, from Middle English schal, from Old English sċeal, from Proto-West Germanic skulan, from Proto-Germanic skulaną, from Proto-Indo-European sḱel-, from Proto-Indo-European ḱelh₁- — to warm up, to be hot; to warm up, be hot.

shall've (English): shall have (with have as auxiliary verb)

Definitions

  1. shall have (with have as auxiliary verb)

Ancestry of “shall've”, step by step

shall've traces back through two separate lines of ancestry.

via English shall

StepLanguageWordMeaning
1Englishshall"I shall sing in the choir tomorrow"; "I hope...
2Middle Englishschal
3Old Englishsċeal
4Proto-West Germanicskulanto owe, to be obliged
5Proto-Germanicskulanąto owe; to be obliged to, have to; shall, will,...
6Proto-Indo-Europeansḱel-to be obligated, owe
7Proto-Indo-Europeanḱelh₁-to warm up, to be hot; to warm up, be hot

via English ’ve

StepLanguageWordMeaning
1English’vein its sense marking the perfect or retrospective aspect
Every word from Proto-Indo-European ḱelh₁-
shall've — Etymology, Origin & Word History | Etymology Explorer