Semantic change happens in all languages, even in that slowest-changing of all Indo-European languages Icelandic, which is nearly mutually intelligble with Old Norse. It is driven at least in part by changes in the world around us, as predicted by the Sapir-Whorf hypothesis. It is also motivated by fashion, sociolinguistic and psycholinguistic factors, and by the fact that language doesn't like synonyms, i.e. if you have two words meaning the same thing, one of the moves a bit so that both remain useful and distinct.

A fine example often quoted is Old English gesaelig, which meant "happy, prosperous" and moved through "blessed, pious, innocent" (C12), "harmless, pathetic" (C13), "weak, weak-willed" (C14), "feebleminded, foolish" (C16), to (Modern English silly) "dizzy, dazed, insensible" as in knocked silly (C19) to "trivial, pointless" and "ridiculous, laughable" (today). The cognate German word, selig, means "blessed, happy" (as in Selig sind, die da Leid tragen, "Blessed are they that mourn", Ps. 25 : 6).

"Gay" is an example of a euphemism that once provided a fig leaf to cover something people didn't want to talk about or admit existed. It has become respectable because of the change in attitudes about those things, not because of the change in meaning of the word itself. But what has happened is that the original meanings of the word, "merry, jolly; brightly-coloured" have given way and it's no longer usual to use the word in those senses. An originally similarly-meaning word, merry, came during the 19th century to mean "pissed". Usually euphemisms go out of fashion and disappear, however.

I think I wrote about this somewhere before, but English grammar, being very analytic (i.e. not inflecting words much but using word order to convey sentence structure) allows words to change their functions easily. For example, modern social media usage allows "like" to be used as a noun and "heart" as a verb, despite there existing perfectly good words of the "correct" part of speech already ("approval" and "love" respectively). One of our favourite words on these fora is s***(e) but despite properly being a noun it is often used as an adjective: "How s***e were we today?" This can happen because English grammar can let you actually not be able to tell whether it's a noun or an adjective. "The ref was s***e today". Is s***e here a noun complement of be, or a predicate adjective? (once upon a time we might have required the latter to be s***ty, but actually I don't think that means the same any more: "covered in s***e" rather than "unfavourably comparable to s***e" ). Oh, and you can use it as an adverb too. "I thought Bloggs played s***e today". Does that mean the same as "... played like s***e"? I don't know. Probably the speaker was taking a shortcut, but you might say that the former looks like a metaphor and the latter like a simile.

Edited by chateauferret (24 Sep 2018 10.26pm)

My mate was recently made redundant so that's stopped me going down to Sittingbourne on a daily basis now

I am glad a never started a thread on this subject you would have blown me out of the water.

I wonder how many men end up raising another bloke's child without realizing it?

Some women are just too gorgeous to be kept to just one man.

Accept my bird that is.....She's just below gorgeous enough to keep to this one.

Edited by Stirlingsays (01 Oct 2018 12.44pm)