"Boggle" is an ancient word

It is amazing how ignorant I am of the English language. I have heard the word "boggle" used for years, usually in the expression, "That boggles my mind." I had just assumed it was some modern slang expression. However, tonight I ran into it in the Bible Commentary by the English theologian John Gill, who died in 1771. So, I looked it up in Skeat's Etymological Dictionary and found that it means "to start aside, swerve for fear," and probably had its origins in Welsh words meaning "a spectre," "a scarecrow," "a threat," and "to scare."