-in

In Shaetlan the present participle is indicated with the suffix -in (pronounced /ən/), as in He's rainin ‘It's raining’. It derives from the Old English -ende which in turn derives from the Proto-Germanic form *-andz. In the Southern English dialects the Old English form weakened to -inde and by the 13th C it was increasingly confused with the suffix -ing (Old English -ing/-ung) that formed nouns from verbs (such as weddung 'wedding'). This is why Standard English now has the same form for both functions. The descendants of Northumbrian Old English, however, such as Scots, never confused the two endings. To claim that the pronunciation of swimmin and singin with -ən is "incorrect" or "sloppy" is therefore historically unjustified and uninformed.