I have somehow picked up the use of the two different forms "thy/thine" from the KJV Bible, and I thought I knew the rule. Use thy before consonants and thine before vowels or before words starting with the sound [h].
There are plenty of instances of thine heart or thine hands in the KJV for example, and while doing a translation from Greek into KJV style English, I almost went along with thine whole heart, since whole, just like hand and heart, starts with the same sound. Right? Well, on second thought I just thought I'd check to see if I find any instances of it, and I was surprised to find:
If thy whole body therefore be full of light, having no part dark, the whole shall be full of light, as when the bright shining of a candle doth give thee light. KJV
I disagree with sites that say
** "Thy" and "thine" are archaic forms corresponding to "your" and "yours" respectively. Use "thy" where you would use "your" (but see note at end of answer) and "thine" where you would use "yours".
because it is very clear to me that thine can definitely mean both your and yours. One answer to this question from the ELU agrees with me, but it does not fully address the phonetic problem of words starting with the sound [h].
Does anyone know the rule? Is it actually a phonetic rule, or an orthographic one?