Where does “that's” come from?

that's (English) comes from English ’s, from English Kingstown, from English town, from Middle English toun, from Middle English ende, from Old English ende, from Proto-Germanic andi, from Proto-Indo-European h₂énti — on, onto.

that's (English): whose, of which

Definitions

  1. whose, of which

Ancestry of “that's”, step by step

that's traces back through two separate lines of ancestry.

via English ’s

StepLanguageWordMeaning
1English’s
2EnglishKingstownOS grid ref NY3959
3EnglishtownA settlement; an area with residential districts,...
4Middle Englishtountown
5Middle EnglishendeThe end or finishing of a thing; the terminal...
6Old Englishendeend, limit, border, corner
7Proto-Germanicandiin addition, furthermore, and
8Proto-Indo-Europeanh₂éntiopposite; near; in front
9Proto-Indo-Europeanh₂éntsforehead; front
10Proto-Indo-Europeanh₂ent-face; forehead; front
11Proto-Indo-Europeanh₂en-on, onto

via English þat

StepLanguageWordMeaning
1Englishþatso, so that, in order that
2Middle EnglishþatAlternative form of that
3Old Englishþætnominative/accusative neuter singular of se: the;...
4Proto-Germanicþatnominative/accusative singular neuter of *sa
5Proto-Indo-Europeantóddemonstrative pronoun; that; it
6Proto-Indo-Europeanto-it; that; the, that
7Proto-Indo-Europeanthis; that
Every word from Proto-Indo-European h₂en-