Why are skew and spew spelled with ew while spume is ume?

You're right to notice the inconsistency in spelling! It's true that English spelling can be quite illogical at times. The reason for the different spellings of "skew," "spew," and "spume" lies in the history of the English language and how words have evolved over time.

* "Skew" and "Spew": These words are related to the Old English word "sceowan," meaning "to look askance" or "to vomit." The "ew" spelling reflects this common ancestor.

* "Spume": This word comes from the Latin "spuma," meaning "foam." The "ume" ending is a result of the Latin influence on English, particularly in scientific and technical vocabulary.

In short, the different spellings are due to the different origins of these words.

Here's a helpful way to remember:

* "Skew" and "Spew" are both related to Old English words with "ew."

* "Spume" is related to Latin words with "ume."

Of course, English is a complex language with lots of exceptions and quirks!