The word "thy" is a reduced form of the Middle English "thin," which was the genitive (possessive) form of the pronoun "thou." It originates from the Old English "þīn," meaning "of thee" or "your." This Old English form is derived from the Proto-Germanic þīnaz, a possessive pronoun built on the base of the second-person singular pronoun. The word's journey reflects the simplification and phonetic erosion common in high-frequency grammatical words, with its modern meaning and archaic status stemming from the historical displacement of the singular "thou/thee/thy" by the plural "you/your" for general address in English.

N/A