how: [OE] How belongs to the large family of question-words which in Indo-European began with qw- (as in English quantity, query, etc). The phonetic descendant of this in prehistoric Germanic was khw-, which in modern English is represented by wh-. How itself comes from a West Germanic adverb *khwō formed from the base that also produced English what and who; like who it has lost its /yingyu/ sound, but since who did not lose it until considerably later the spelling wh remains as a reminder of it.
The how! with which North American Indians supposedly greet each other is not the same word, incidentally. It is an imitation of a Sioux word, such as Dakota háo or Omaha hau. => what, who
