Learn English – Why do we spell the word “who” with a silent “w” when it isn’t needed

The spelling "who" was originally used simply because, in past time periods, this word was pronounced with a "wh" sound. To be clear, by "a "wh" sound" I mean a sound that is different from either "w" or "h" on its own. Although many varieties of English have lost "wh" as a distinct sound, replacing it with plain [w], the digraph "wh" used to (and in some accents still does) have a value that can be transcribed as /hw/, or written with the special symbol [ʍ] if we interpret it as a single sound.

Many aspects of modern English spelling derive from Middle English pronunciation. Analogy with the spelling of other words probably contributed to the continued use of "wh" in spelling even after people started pronouncing the word with a simple /h/ sound. "Who" is one of the many question words starting with wh- in English.

Here is a brief explanation of why who lost its /w/ sound. The sound [w] is made by rounding the lips. The pronunciation of the word "who" evolved over time to have a rounded vowel sound, and the presence of a rounded vowel sound caused people to stop hearing a separate rounded consonant at the start of the word. This has happened in other words, most obviously two.

The question word how lost its /w/ sound for a similar reason, but much earlier, so it has a spelling without "wh".

Unfortunately, irregular spellings in English aren't always etymological. Because of the confusion between "h" and "wh" before rounded vowels, a few words pronounced with a simple /h/ sound are spelled with "wh" before "o" even though, from an etymological perspective, they would be expected to just have "ho". An example is whole, which is etymologically related to heal.

A few blog posts that relate to topics brought up in the comments:

• "Hwæt about WH?", by Mark Liberman, 2011 April 13

• "The Secret Ways of Weak Forms: Here Comes a New ’Un", by Piotr Gąsiorowski, 2013 February 07