Where does “tyst” come from?

tyst (Middle Welsh) comes from Proto-Brythonic *tɨst, from Latin testis, from Latin terstis, from Latin trīstis, from Proto-Indo-European tristh₂s, from Proto-Indo-European steh₂- — to stand.

Ancestry of “tyst”, step by step

Step	Language	Word	Meaning
1	Proto-Brythonic	*tɨst	—
2	Latin	testis	witness; one who testifies or attests; testicle
3	Latin	terstis	—
4	Latin	trīstis	sad, unhappy, melancholy, morose
5	Proto-Indo-European	tristh₂s	a third party standing, after the two parties to...
6	Proto-Indo-European	steh₂-	to stand

Words derived from “tyst”

tyst
tystiolaeth
tystio
tysteb
tystlythyr
tystysgrif
gwrthdystio
tystiolaethu

Every word from Proto-Indo-European steh₂- →Every word from Proto-Indo-European tristh₂s →Every word from Latin trīstis →