Naish: Ignatius.
Source: LS1

nallered: captured, arrested (a fusion of nailed and collared)
Source: LS1

nance: an effeminate male. Also: a Nancy
Source: LS2

Nanny Goat(rhyming): coat
Source: LS3

nark, to: to give information to the police about a crime
Source: LS4

Nark: a dispute, a quarrel

Narky: irritable, bad-tempered
Source: LS2

Nash, Ther: either the Grand National horse-race, or the National Assistance Board
Source: LS2

Nat King, der(rhyming): the dole, collecting social benefits
Source: LS3

naughty pin(sometimes naughty legs): legs which are not particularly shapely
Source: LS3, SL

necessary, the: a euphemism for animal droppings, sometimes much sought after by gardeners
Source: SL

necessary place, the: the lavatory
Source: TIM

needle match: a match involving personal or traditional club rivalries or resentments
Source: GTH

Needs his head felt: should see a psychoanalyst
Source: SL

neeps( as in "mashed neeps"): turnips
Source: SL

Nellie(also Nelly): an effeminate or homosexual male; also a feeble or soft person
Source: DS

Nelly, not on your: highly unlikely
In rhyming slang, the full phrase was "not on your Nelly ruff," which rhymed with puff, meaning the air in your lungs or the breath of life.
Source: OED

Nelson's Blood: rum. After the Battle of Trafalgar, Nelson's slain body was put in a barrel of rum, pending its return home. Tradition has it that when the body was removed for a proper ceremonial burial homeside, several sailors came upon the barrel and finished off the contents. They caroused on Nelson's blood in that sense, and from then on among Royal Navy sailors, rum had a new name.
Source: SL

Nesh: not very hardy, not able to stand the cold.  In Lancashire, nesh means tender, weak, delicate, soft.
Sources: SL, GLD

Netherfield Road Navy: the bands of the Loyal Order of Orange Lodges, usually dressed in quasi-naval uniforms.  Cf. "The Good Ship Neverbudge" on this list.
Source: SL

neuralgic: Liverpudlianism for nostalgic
Source: SL

never-never, the: the weekly installment plan.some say it refers to the intention not to pay the rest of what is owed, others say that "never-never" refers to the never-ending payments.
Sources: MV, TMD

News of the Screws: one of several names for a newspaper for National Servicemen. Other names: Whore's Gazette, Red Light News, Piccadilly Part Two Orders, and Screws of the World
Source: PM

Niagra Falls(rhyming):testicles
The rhyming component should be obvious
Source: LS3

nick, the: prison, or police station, or a military guard room. Nick can also mean an "arrest."
Source: LS4

nick, ther: the Walton Jail
Source: LS2

Nick: steal
Source: LS1

Nick off, to: to run off for some illegitimate or larcenous reason.
Source: SL

nicker, a: a one pound note
Source: LS1

Nickers: cigarette butts. Spiegl thinks this comes from the habit of nicking(pinching) a cigarette to put it out and keeping it for future use.
Source: LS2

nickers in a twist, to get:  to get strongly upset about something or other
Source: SL

Night-man: social worker who comes at night to check on overcrowding in slum dwellings
Source: Shaw ML

nig-nog: an insulting reference to a person of color
Source: SL

niggers' eyeballs: now no longer heard, a highly objectionable term for semolina pudding.  Semolina, or some other unflavored pudding, if sprinkled with raisins, was called "niggers in the snow."
Source: SL

night on the tiles: refers to a night of drinking on the bar room tiles
Source: SL

Nin. Me nin. My grandmother, or favorite aunt, or just a friendly neighbor.
Source: LS1, Moloney

nip out to: to go out, sometimes stealthily, as in "to nip out for a pint."
Source: SL

Nippy: a waitress.  The word probably refers to how fast a waitress was expected to perform her duties.
Source: SL, ODS

Nix, to keep: to keep lookout for the police
Source:  ST

No-boot brigade(obsolete): the Liverpool underclass
Source: ALS

noak, to(obsolete): to keep watch (criminal)
Source: A

nob(obsolete): someone of wealth or high social position; the term usually implies contempt.
Source: ODS, A

nobble, to: to tamper with, also to catch or to trap in police parlance.  Nobble meant to drug a horse to keep it from winning; it referred generally to reducing someone's ability or power.
Source: SCHUR, SI, SL, ODS

nobs( as in "I'll be there with nobs on"): a very general intensifier, conveying the sense of "for sure," or "indeed."
Source: SL

noddy bike: small motor-scooter formerly used by police on patrol
Source: LS4

Noddy: a fool, a simpleton, a noodle
Partridge notes that in the Enid Blyton stories there is a hero who is a rather stupid elf called Noddy
Source: DS

Nogsie: Norris Green Park
Source: SL

Nomark: a nonentity, a person who draws no attention
Source: SL

Nonce: a sex-offender
Source: LS4

Nook, The:  a very popular bar in Liverpool's Chinatown, whose gambling dens were freqently raided.  The occupants protested that there was no gambling going on there, but the problem was more than semantic.
Source:SL

North and South (rhyming): the mouth,
Source: LS3

nosh: to eat (usually, to eat ravenously)
Source: LS2

Not the full quid: mentally deficient. Also: not the full shilling
Sources: BUABS, SL

Not wert a light. Of no value.
Source: LS1

Not elevenpence for a shilling: a foolish person (insult)
Source: SHAW II

Not too foul: beautiful
Source: LS3

Nowse(also nous): skill, flair, knowledge, good sense, intelligence
Spiegl thinks the word comes from the Greek nous, or mind, which would make it an unusual survival in popular speech. It shows up in Lancashire too, and is Greek, but probably by way of university slang.
Sources: LS2, GHTL, GLD

nowt: nothing
Source: LS2

nuck noses:  noses flattened from being pressed against a window
Source: SL

Nudger: long sandwich made from an elongated bread roll. Spiegl notes that "nudger" is a dysphemism for penis, so the term may be unwelcome in the "better" establishments.
Sources: LS1, LS3

Nut, to do one's: to be or get angry, to go berserk
Cf. "Doin' me ed in"
Sources: OED, GYW

Nut-cracker: policeman (nut being a reference to heads cracked)
Source:  ML

Nut-pox: Ringworm
Source: LS2

nutmeg, to: in soccer, to send the ball through the legs of an opposing player or goalie, who then loses face.
Source: GTH

Nutmeggin': head-butting the face
Source: LS4

nutmegs: testicles
Source: GTH

nutting: head-butting
Source: GTH

Nutty slack: coal slack or leavings in small lumps or nuts
Source:OED