neuter possessive pronoun; the modern word begins to appear in writing at the end of 16c., from it + genitive/possessive ending 's (q.v.), and "at first commonly written it's, a spelling retained by some to the beginning of the 19c." [OED]. The apostrophe came to be omitted, perhaps because it's already was established as a contraction of it is, or by general habit of omitting apostrophes in personal pronouns (hers, yours, theirs, etc.).
The neuter genitive pronoun in Middle English was his, but the clash between grammatical gender and sexual gender, or else the application of the word to both human and non-human subjects, evidently made users uncomfortable. Restriction of his to the masculine and avoidance of it as a neuter pronoun is evidenced in Middle English, and of it and thereof (as in KJV) were used for the neuter possessive. Also, from c. 1300, simple it was used as a neuter possessive pronoun. But in literary use, his as a neuter pronoun continued into the 17c.
雙語例句
1. Generosity is its own form of power.
別低估了慷慨的力量。
來自美劇《紙牌屋》
2. The council recently drew fire for its intervention in the dispute.
委員會最近因為介入該起爭端而遭到批評。
來自柯林斯例句
3. "Kathleen" was, as its 1892 subtitle asserted, "An Irish Drama".
正如1892年劇本的副標題所強調的，《凱瑟琳》是一部“愛爾蘭戲劇”。
來自柯林斯例句
4. The club has moved its meeting to Saturday, January 22nd.
俱樂部已經把會議日期改到1月22號，星期六。
來自柯林斯例句
5. Dense smoke swirled and billowed, its rank fumes choking her.