Emily Dickinson Lexicon

MY, a. [pronom. adj. contracted from migen, mine. Me was originally mig, and the adjective migen. So in L. meus. See Mine.]

Belonging to me; as, this is my book. Formerly mine was used before a vowel, and my before a consonant; my is now used before both. We say, my book; my own book; my old friend. Mine is still used after a verb; as, this book is mine.