Words and phrases are often used in conversation, especially by the young, not as significant terms but rather, so far as they have any purpose at all, as aids of the same kind as are given in writing by punctuation, inverted commas, and underlining.
It is a phenomenon perhaps more suitable for the psychologist than for the philologist.
Words and phrases so employed change frequently, for they are soon worn out by overwork. Between the wars the most popular were DEFINITELY and sort of thing. One may suppose that they originated in a subconscious feeling that there was a need in the one case to emphasize a right word and in the other to apologize for a possibly wrong one. But any meaning they ever had was soon rubbed off them, and they became noises automatically produced.
Their immediate successors have been actually (pronounced akshally) and you know. Actually, says the Oxford English Dictionary, may be added to vouch for statements which seem surprising, incredible, or exaggerated. That is how Mrs. Nickleby and Mr. Pyke used it.
'"I had a cold once," said Mrs. Nickleby, "I think it was in the year 1817 ... that I thought I should never get rid of; actually and seriously that I thought I should never get rid of". . . . "And I'll tell you what", said Mr. Pyke, "if you'll send round to the public house for a pot of mild half-and-half, positively and actually I'll drink it."'
Many people today seem to find it impossible to trust any assertion, however commonplace, to be believed without this warranty. We have all had experiences like that recorded by Ivor Brown:
'I met some young people recently who used actually in almost every sentence. "Are you living in London?" "Actually I am." "Actually we must be going now."' 'Actually', he adds, 'I did not mind if they did.'
The now ubiquitous you know (cf. the obsolete dontcherknow) seems to be a compendious way of saying 'I know I am expressing myself badly, but I am sure you are intelligent enough to grasp my meaning'.
Well is a permanent member of the class of words thus used, and Incidentally is having a long innings. The 'interrogative expletive' what, as the Oxford English Dictionary calls it, quoting "Goodbye Miss Thornton", awfully jolly evening, what? , was once fashionable, but has had its day.