No one will argue The Beatles' significance in popular music (actually, some may, but they're idiots). Their impact on the lexicon is less clear (using the word 'na' 217 times in the lyrics of "Hey Jude" really doesn’t count - there's some trivia for you). Incidentally, the Oxford English Dictionary does include the word "na" with the meaning "than," citing JM Barrie's Window in Thrums: "The big ane’s bigger na usual." – but it is, of course, extremely unlikely that Paul intended any reference.
A quick dip into the OED shows that if
John and Paul hadn't bumped into one another in Woolton on that sunny July day
in 1957, we would have been deprived of words such as "Beatlesque," derivative as it is. Even "Beatle" itself has an entry, attributed to "hair-style or other characteristics of The Beatles or of their
imitators."
Look more deeply for potential surprises: the word "grotty," shortened form of "grotesque," may have been used before the Beatles , but when George says it in A Hard Day’s Night the word became instantly colloquial. Indeed, the first citation currently given in the OED is from John Burke's novelization of the film published in 1964 (like all novelizations, a masterpiece). Also in 1964 came what was the first known use of the word moptop ("a rather shaggy hairstyle popularized by members of the British band The Beatles; a person with such a hairstyle"). The earlier use (by some 75 years), "mop-topped," is a reference to rose trees rather than the Liverpudlian unkempt.
You don’t have to stray too far alphabetically
from "moptop" in the OED before you hit "mod" ("A
young person belonging to a subculture preoccupied with smart, stylish dress,
characteristically associated with riding motor scooters and listening to soul
music. Freq. contrasted with rocker"). A question the Beatles
often faced in the mid-60s was whether they were mods or rockers. "I'm a mocker" was Ringo's reply in A Hard Day’s Night, and it was a
typical Beatles response. When they weren’t selling hit records, the Beatles
enjoyed nothing better than a good pun – or, more often, a bad one, depending
on one's stance. Even the name of the band was a pun combining references to
beat music and fellow entomological group Buddy Holly and the Crickets.
The wordplay wasn't always sophisticated, but it was a
constant in the Beatles' career: the title of their seventh studio album, Revolver, was
a pun (the vinyl record revolves, geddit?), as was the title of their
sixth: Rubber Soul. The latter was derived from the phrase “plastic soul”,
which Paul McCartney muttered after an out-take from
"I’m Down" in 1965. The first known use of plastic to
mean artificial or superficial is dated two years earlier in
an article by British newspaper The Daily Telegraph, pondering
"whether plastic houses might not connote plastic people."
When the Beatles freed themselves from EMI in 1968 by setting up their own company – chiefly a record label
with an optimistic number of subsidiary divisions covering electronics,
publishing, films, and retail (EMI and Capitol remained the chief marketing and distribution entities) – they reached for yet another pun by naming it Apple
Corps. Paul was delighted by the cleverness of the
joke, repeating it several times to the press to ensure they understood.
John played the wordsmith game when he published In His Own Write and A Spaniard in the Works in
1964 and 1965 respectively (Americans don't use the term spanner, so the pun is lost). These contain an amalgam of short stories, nonsense poetry, and
doodles, with Edward Lear and Lewis Carroll being among Lennon's influences: take, for example, the lines: "He is putting
it lithely when he says/ Quobble in the Grass,/ Strab
he down the soddieflays." John clearly had an admiration for these writers,
referring to Lear in "Paperback Writer:" "It's based on a novel by a
man named Lear" – and basing "I Am The Walrus" somewhat loosely on
Carroll's "The Walrus and the Carpenter." Maintaining the literary theme,
this latter song also included an explicit reference to another writer:
"Elementary penguins singing Hare Krishna; man, you should have seen them
kicking Edgar Allan Poe."
Na na na na na na na...