WHAT, INTERROGATIVES?

Today I'd like to talk about all the wh- interrogative words in English. If you look at their etymologies, they all follow a similar pattern:

• Who came from Old English hwa
• What came from Old English hwæt
• When came from Old English hwenne
• Where came from Old English hwær
• Why came from Old English hwy
• How came from Old English hwu
• Which came from Old English hwilc
• ​Whether came from Old English hwæþer

All of them started with a devoiced w sound, but now some start with a h sound and some start with a w sound (just looking at phonology, ignoring the spellings). The difference is that the initial [w] words in Old English started with hw followed by vowels made in the front of your mouth, while initial [h] sounds like those in who and how started with hw followed by a vowel closer to the back of your mouth. Through Proto-Germanic, all of the words go back to a Proto-Indo-European word sounding like kha, and then Grimm's Law uniformly shifted the sound to the Old English hw​.