en_tn_lite_do_not_use/isa/52/15.md

Yahweh continues speaking about his servant.

startle

to surprise suddenly, possibly from fear, making someone move without thinking about it

That which they had not been told

AT: "That which no one had told them" or "Something no one had told them" (See: rc://en/ta/man/translate/figs-activepassive)