Lenis consonants normally preceded by long vowels
High German has a strong tendency that lenis consonants are preceded long vowels (or diphthongs, which count as long vowels in this regard). This is because short vowels followed by lenis consonants were lengthened, cf. Middle High German lësen vs. modern standard German lesen ‘to read’:
lësen [ˈlɛsən] → lesen [ˈleːzen]
Words with short vowels followed by lenis consonants are loans from Low German or from other languages that occured after this lengthening had occured, e.g. «Buddel» ‘bottle’, «Flagge» ‘flag’, «schwabbeln» ‘to wobble’, «Dussel» ‘dimwit’, «Puzzle» ‘jigsaw puzzle’, «Schlamassel» ‘shemozzle’.
Consonant pronunciation not affected by doubling
Almost all German consonant letters are pronounced the same whether or not they are doubled. What changes is not the pronunciation of the doubled consonant, but of the preceding vowel (this is the same in English or Dutch):
Schafe [ˈʃaːfə] ‘sheep’ – schaffe [ˈʃafə] ‘create’
Stele [ˈʃteːlə] ‘stele’ – Stelle [ˈʃtɛlə] ‘place’
Rate [ˈraːtə] ‘rate’ – Ratte [ˈratə] ‘rat’
Historically, this used to be different. Doubled consonants used to be pronounced longer in Middle High German. After short vowels followed by lenis (short) consonants had been lengthened and after consonant length had been lost, the doubling of consonants has taken on a new meaning: it no longer means a long pronunciation of the consonant itself, but a short pronunciation of the preceding vowel.
Doubling of S affects pronunciation
The letter S is different from all other German consonant letters. When it is doubled, its own pronunciation changes (this is often the case in English as well):
Hase [ˈhaːzə] ‘hare’ – hasse [ˈhasə] ‘(I) hate’
Here we see that the single ⟨s⟩ is pronounced as a lenis [z], whereas the doubled ⟨ss⟩ is pronounced as a fortis [s]. Now in loans like «Dussel», this is a problem: we have two orthographic rules that contradict each other:
- A short vowel must be followed by a doubled consonant.
- A doubled ⟨ss⟩ is a fortis [s], not a lenis [z].
Apparently, the first rule wins over the second one, since we spell the word with ⟨ss⟩ in spite of the lenis [z].
Why is S different from other consonants?
(This section is speculative.)
It is surprising that S is the only German consonant pronounced different when doubled. This is especially striking when we consider the difference from F. Both F and S are similar sounds that have comparable histories. Yet the pronunciation difference between FF and F was lost:
hûfen → Hauffen → Haufen ‘heap’
snûven → schnaufen ‘to snuffle’
By contrast, the pronunciation difference between SS and S has been kept:
heizer → heiszer → heißer ‘hotter’
heiser → heiser ‘hoarse’
I do not know the reason. Here are some factors that might be considered:
- It is common in neighbouring languages that ⟨s⟩ is voiced [z], whereas ⟨ss⟩ is voiceless [s].
- There is no other candidate for writing lenis [z] in German (⟨z⟩ stands for [ts]). This is different from F, where ⟨w⟩ has become the voiced counterpart.
- In the actual pronunciation of many speakers, the contrast might not exist at all: they will pronounce «heißer» exactly like «heiser», or they will rhyme «Diskussion» with «Konfusion». The differentiation might be a learned spelling pronunciation.
- A factor that might have helped in retaining the different pronunciation of ⟨ss⟩ might be the existence of the SZ ligature in the fraktur script, from which the modern letter ⟨ß⟩ was derived in the 1902 spelling reform.