What is thyself? How to use in English

The word "thyself" is a historical form of the pronoun "yourself" and "myself" in older English. Its origins can be traced back to the Old English language, where it was spelled as þæsclīf or þēsclīf. The prefix "þæ" or "þē" in Old English served as an emphatic particle, which added emphasis to the pronoun "self". The grammatical function of this prefixed form was to indicate that the person referred to was identical to the subject of the sentence. For example, "Thā Stuart cast a great stone, but þæsclīf nilt ne wolc" translates to "Theoste cast a great stone, but himself did not want or could not will it." Over time, the Old English language evolved into Middle English, and the spellings of the words changed as well. By the 15th century, "thyself" had become a common form in Middle English, with hyphenated spellings like "thenselfe" and "thynself". As English continued to develop in the modern era, "thyself" became less common, replaced by "yourself" and "myself" in standard usage. Today, "thyself" is primarily used in poetic or historical contexts as a throwback to the language of an earlier time.