Till and until are both old in the language and are interchangeable . . .

Also

First recorded before 900; Middle English; Old English (north) til “to,” from Old Norse til “to,” . . .

Many people assume that till is a misshapen abbreviation of until... However, till is not a shortening of until. It actually predates the longer word.

The above paragraph is from Merriam-Webster:

https://www.merriam-webster.com/words-at-play/should-you-use...