French scribes changed the common Old English letter pattern "hw" to "wh", largely out of a desire for consistency with "ch" and "th", and despite the actual aspirated pronunciation, so
that hwaer became where, hwaenne became when and hwil became while. A "w" was even
added, for no apparent reason, to some words that only began with "h" (e.g. hal became
whole). Another oddity occurred when hwo became who, but the pronunciation changed so
that the "w" sound was omitted completely. There are just some of the kinds of
inconsistencies that became ingrained in the English language during this period.