Two processes at work: pre-cluster shortening followed by wyn-dropping.
pre-cluster shortening:
break ~ breakfast
green ~ Greenwich
goose ~ gosling
waist ~ waistcoat
wyn-dropping:
historical one > an
husband > hussy
inwards > innards
always > allus
will > 'll
-wich, -wick > -ich, -ick
In his Historical Wyn Dropping, Jack Windsor Lewis says
Placenames abound throughout Britain ending -wich and -wick most of which retain their spellings with w but have long dropped their wyns eg Alnwick, Berwick, Bromwich, Chiswick, Greenwich, Harwich, Keswick, Norwich, Smethwick, Warwick, Woolwich. Some have restored their wyns if they ever lost them eg Droitwich, Hardwick, Ipswich, Nantwich, Sandwich and Lerwick. Surnames are more likely to have been re-spelt more phonetically as in the cases of Garrick and Crummle(s) the latter of which also exists as Cromwell.
Check his note on Current Wyn Dropping.