The letters are actually the first three letters in the name of Jesus as spelt in the Greek alphabet, which has much in common with the latin alphabet, but differs enough to cause confusion. The first letter is an iota, corresponding nicely to I, and the third is a sigma, corresponding to S. The middle is an eta, a vowel that neither English or Latin has, and in its capital form it looks like an H, but is pronounced nothing like an H. As most people encountering the three letter abbreviation do not think of Greek, alternate explanations have sprung up over the years.
This monogram also has been carried over into Lutheran churches.
Whew, thanks, Hiero. I was wondering how many incorrect explanations we would go thru before someone gave the right one.
IHS is a “monogram” or abbreviation for the name of our Lord Jesus; it’s the first 3 letters of His name in Greek. It’s that simple.