etymology - Was "book" to "beek" as "foot" is to "feet"?

"Foot" is a curious word in English because it is pluralized in an unusual way; the "oo" in the word is changed to "ee". Did this once use to be a standard way of pluralizing things in English (or a language that contributed to English), which would mean that the plural of "book" was "beek" instead of "books"? Or, is "feet" just a one-off?

Answer

Whenever you find an O (or some other back vowel like A or U) in one form of an English word and an E (or some other front vowel like Æ or I) in the corresponding place in another, you have two suspects to interrogate.

1. If the two words are not from the same language, but from two separate Indo-European languages, like Latin and Greek (e.g, ped-al from Latin and pod-iatrist from Greek, both roots meaning 'foot' — the p ~ f and d ~ t alternations are Grimm's Law in action), then what you're seeing is E–O Ablaut. Proto-Indo-European often alternated between an "E-grade" and an "O-Grade" form for morphology, and various daughter languages inherited various words. Sort of like the distribution of family furniture when the parents die. That's not what happened here, however.




2. If the two words are from English, and not borrowed, then what you're seeing is Umlaut. This term refers to changing a back rounded vowel [o, u] to the corresponding front rounded vowel [œ, y] in anticipation of a front vowel [i, e] in the next syllable. This is a common Germanic feature, and is still productive in German, where there are special vowel symbols (ü, ö, ä, called U-umlaut, O-umlaut, and A-umlaut) that represent this phenomenon, and these sounds. Umlaut is the guilty suspect.

In English, this happened to many normal plurals because of the E in the regular plural suffix -es. That E was pronounced in Old English and Middle English, but not in Modern English; however the root vowel had been changed already and is maintained in some, but not most, of the nouns.

The original Old English (or possibly Proto-, West, or Low Germanic) of goose/geese (in Modern English [gus/gis]) was [go:s/go:ses]. There were several steps in the derivation:

• dropping final s ⇒ [go:s/go:se]


• fronting the o: to œ: by umlaut ⇒ [go:s/gœ:se]


• derounding œ to e ⇒ [go:s/ge:se]


• final e going silent ⇒ [go:s/ge:s]


• Great Vowel Shift raising all long vowels one notch ⇒ [gu:s/gi:s]


• losing long vowels ⇒ [gus/gis]

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Edit:
In this medium, where writing and typography has to express speech and sounds, I use italics and boldface like this:

• I use plain italics only for citing examples and titles. Never for emphasis.


• I use boldface for emphasis. These are words that would be LOUD in my speech.


• I use bold italics for technical terms, usually with capitals, and links if I have them.


• I also use bold italics in examples to point out individual parts that get mentioned in the text.