The words iPod, iPad, iTunes, iVillage etc, with their i- prefix standing for 'internet' or perhaps something else, seem to epitomise the 21st century. Not a bit of it! There are dozens of words in the Oxford English Dictionary from the 9th, 10th, 11th and 12th centuries that have the prefix i-: i-be (an old form of the verb 'to be'), i-creoiced (crossed), i-deme (to judge, deem), i-freond (friends), i-go (to go), i-hitte (to hit), i-hwat (everything), i-ken (to make known), i-mete (to meet), i-same (together), i-wepen (weapons), i-wis (certain) and many others.
The i- was a feature of Old English (before the Norman Conquest) and the first centuries of the Middle English period (up to about the 13th century). It later changed to y- so you had ygo and ywis, for instance. The words were written either with the i as a separate word, or hyphenated, and the Oxford English Dictionary has chosen to write them with a hyphen. This prefix was the equivalent of the German prefix ge- (remember that English is a Germanic language because of its structure). It was used to begin collective nouns (as weapons above), adjectives, adverbs and verbs.