IyoudaoicibaDictYouDict[I 词源字典]
I: [OE] Essentially all the Indo-European languages share the same first person singular pronoun, although naturally it has diverged in form over the millennia. French has je, for example, Italian io, Russian ja, and Greek egó. The prehistoric Germanic pronoun was *eka, and this has produced German ich, Dutch ik, Swedish jag, Danish jeg, and English I. The affirmative answer aye ‘yes’ [16] is probably ultimately the same word as I.
=> aye, ego[I etymology, I origin, 英语词源]
I (pron.)youdaoicibaDictYouDict
12c. shortening of Old English ic, first person singular nominative pronoun, from Proto-Germanic *ek/*ik (cognates: Old Frisian ik, Old Norse ek, Norwegian eg, Danish jeg, Old High German ih, German ich, Gothic ik), from PIE *eg-, nominative form of the first person singular pronoun (cognates: Sanskrit aham, Hittite uk, Latin ego (source of French Je), Greek ego, Russian ja, Lithuanian aš). Reduced to i by mid-12c. in northern England, it began to be capitalized mid-13c. to mark it as a distinct word and avoid misreading in handwritten manuscripts.
The reason for writing I is ... the orthographic habit in the middle ages of using a 'long i' (that is, j or I) whenever the letter was isolated or formed the last letter of a group; the numeral 'one' was written j or I (and three iij, etc.), just as much as the pronoun. [Otto Jespersen, "Growth and Structure of the English Language," p.233]
The form ich or ik, especially before vowels, lingered in northern England until c. 1400 and survived in southern dialects until 18c. The dot on the "small" letter -i- began to appear in 11c. Latin manuscripts, to distinguish the letter from the stroke of another letter (such as -m- or -n-). Originally a diacritic, it was reduced to a dot with the introduction of Roman type fonts. The letter -y- also was written with a top dot in Old English and early Middle English, when it tended to be written with a closed loop at the top and thus was almost indistinguishable from the lower-case thorn (þ).