Aleks wrote:Different question but I am wondering about the origin of German using <eu> and <ei> to represent the diphtongs they represent. Why not <ai> instead of <ei>?
From what I can tell, it's a historical spelling. Some instances of /aɪ/ come from /ei/, which was spelt <
ei> and some instances of /ɔʏ/ come from /eu/, written <
eu>. Later instances of /aɪ/ come from /i:/, and likewise later instances of /ɔʏ/ come from /y:/ (maybe? I'm a little uncertain on this one), but there was no orthographic pressure to adopt, say, <
ai> over <
ei> (in the sense that there was no /ai/ <
ei> for /ei/ <
ei> to merge into), so <
ei> stuck around for /aɪ/ < /ei/ and this spelling convention was adopted in turn for /aɪ/ < /i:/.
That's about it as for as I can tell. Old diphthong shifted, but nothing caused any pressure for the spelling to change and that spelling was adopted to represent diphthongs arising from another sound shift.