Ï

I (named i /ˈaɪ/, plural ies) is the ninth letter and the third vowel in the ISO basic Latin alphabet.

In the Phoenician alphabet, the letter may have originated in a hieroglyph for an arm that represented a voiced pharyngeal fricative (/ʕ/) in Egyptian, but was reassigned to /j/ (as in English "yes") by Semites, because their word for "arm" began with that sound. This letter could also be used to represent /i/, the close front unrounded vowel, mainly in foreign words.

The Greeks adopted a form of this Phoenician yodh as their letter iota (⟨Ι, ι⟩) to represent /i/, the same as in the Old Italic alphabet. In Latin (as in Modern Greek), it was also used to represent /j/ and this use persists in the languages that descended from Latin. The modern letter 'j' originated as a variation of 'i', and both were used interchangeably for both the vowel and the consonant, coming to be differentiated only in the 16th century. The dot over the lowercase 'i' is sometimes called a tittle. In the Turkish alphabet, dotted and dotless I are considered separate letters, representing a front and back vowel, respectively, and both have uppercase ('I', 'İ') and lowercase ('ı', 'i') forms.

...
Wikipedia