English as she is spoke (possibly a new series?)

Lots of things fascinate me about the English language, both as spoken in Britain and in its many variants throughout the world, whether when spoken by people for whom it is a first language or those (much more numerous) people for whom it is a second language or purely a business language. So many things have flitted through my mind on this subject over the years; most times I simply note them mentally and pass on. However, a few stick in the mind and that's what this post is about (one at a time though - a whole list in one go might become tiresome); maybe I'll write later posts with other 'gems' or curiosities I have noticed.

OK, to kick this off: some words strike me as faintly ridiculous or incongruous, specially when compared with other words. Example 1:

- 'laughter' is pronounced LAFFTER and generally denotes something happy, joyous even;

- precede with the four letters 'mans', however, and the reamining eight letters are pronounced completely differently - MAN-SLOTTER - and take on a wholly different class of meaning. The same change in pronunciation occurs when the single letter 's' precedes the eight letters.

Whenever I /read/hear/see a report of a murder case in which the crime is classified as 'manslaughter', my usual reaction is to say to myself an ironic MANS-LAFFTER. To say so out loud, however, would lay me open to the charge of crass insensitivity when discussing what is usually a tragic occurrence.

So, why the change in pronunciation? Usually when I have posed such questions before the only response available has been 'just because' or similar. Does anyone have anything more sapient to say on the matter?