OED video notes:

Writing the OED: American English: (Jesse Sheidlower)
 The people in New york are concentrating there time into look at American English slang such as "toy boy" and "boy toy".
the phrase "boy toy" was first popularised by Madonna on her album cover for her song "like a virgin" here she was using it in an ironic sense but nowadays people seem to use it more to describe a boy who is a toy to an older woman.

Writing the OED: New Words: ( Fiona McPherson)
 Fiona is an editor for the OED and she has been looking at the word "charity shop" which she found to not be in the dictionary, a charity shop has two meaning she found during her research in English it means a shop on the high street that sells donated goods for charity, and in American English it means a shop set up to to do work for the poor and this had been around since 1851.
 New words often come from the public via a suggestion in the form of a wire basket which is a slip of paper which you would be found inside the quotation room, this is were the editors go to find suggestion for word and then they research them and possibly enter them into the OED.

The origin of  "Posh" in the OED: (Fiona McPherson)
 The word "Posh" comes from the acronym Port Out Starboard Home, which comes from sea voyages  it was suggested that the best room had better conditions and they were on the port side one way and the starboard side on the way back.

OED appeal for "Disco":
 An appeal is when the OED is asking people for conformation of a word or phrases origins.
In the summer 1964 there was evidence of "disco":
July of that year they found evidence that "disco" was a word that meant a short sleeveless dress  but in August of that year they found examples of "disco" dancing and eventually they found example of the use of "disco's" as in disco tech.

OED appeal for "blue-arsed fly":
 In the modern times its spoken or written in a metaphorical sense when someone says something, but its found to have been first used in 1986 in a new posting from one of the royals, but it seems unlikely that this would be the earliest example.

OED appeal for "in your dreams!":
 In modern times it means the sarcastic interjection when someone says something. This was first used in 1986 in a news room posting but it seems likely that it would have been used before this time possibly in popular culture magazines or newspapers.

Language Change

Lean:

Old English definition of lean was “thin, spare, with little flesh or fat”, whereas nowadays lean can mean a cut of meat (lean meat) or it could mean someone who has a good body structure (tall, lean and handsome).

This means the word has broadened its meaning over the years.

Novice:

In the mid- 14 century the word novice meant a “probationer in a religious order,” In the modern day it simply means someone who is new to somewhere of something. The old French translation was “beginner” so I believe that the word as broadened its meaning because it’s an openly used word for all people who are new to something.

Revolutionary:

The word revolutionary is a noun from the word revolutionist this word is American. In the UK it means pretty much the same thing but it has taken on a more positive meaning, this is called Amelioration.

Lewd:

In old English the word Lewd meant “nonclerical” which is derived from the Vulgar Latin. In the modern day Lewd means something is crude or offensive in a sexual way.

I believe this word has now got a much more of a narrow meaning but also it has a much more of a negative meaning.