A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

get into someone’s skin • get under someone’s skin
get into someone’s skin —(coll.) come to a complete under-
standing of smb.’s inner nature (impersonating a character,
etc.): In the church scene, Miss Rehan won her audience …
but she never really “got into the skin” of Beatrice.
get under someone’s skin —(coll.) 
1
. bother or irritate a person:
John is so annoying at times. He really gets under my skin. 2.
affect a person so that he becomes very interested in smth.:
After a slow start, the play gets under your skin because of its
sympathy with the frustrations of small town life. 3. = get into
someone’s skin: I think you are interested in — character, shall
we say? To get under the skin, as it were, of your criminal.
get it into one’s head • take it into one’s head
get it into one’s head —
1
. realize the significance of smth.: I
wish you would get it into your head, once and for all, that
I’m not made of money. 2. start to imagine or believe smth.
without sufficient grounds: Somehow he got it into his head
that everyone was blaming him.
Note: 
The expression does not correlate in meaning with the
phrase get it through one’s head—figure out smth.; begin to
understand smth.: I never could get it through my head how
a car engine works.
take it into one’s head —
1
. = get it into one’s head 2: Somehow
he’d taken it into his head that his wife was trying to poison
him. 2. decide to do smth.: If I should take it into my head
to tell what I had heard, tremendous mischief could result.
get it off • get it off one’s chest
get it off —(sl.) achieve sexual satisfaction: The entire crew
of the yacht came ashore to get it off.
get it off one’s chest—relieve one’s mind by telling about one’s
problems, etc.: It’s about time we long-suffering Northerners
got it off our chest.