natterjack, n. More fully natterjack toad. A small toad, Bufo calamita, of western Eurasia (now rare in Britain), which has a light yellow stripe down the back and runs in short bursts.

natter, v. intr. Sc. and Eng. regional. To grumble, complain, nag.

1950 W. KEMP Cornkisters 5 “If there's naethin' on earth tae grunt aboot, he'll neatter at the meen.”

colloq. To chatter; to chat aimlessly, idly, or at length.

Jack, n. (As a common noun.) A man of the common people; a lad, fellow, chap; esp. a low-bred or ill-mannered fellow, a ‘knave’. Obs.
1596 SHAKES. Tam. Shr. II. i. 290 A mad-cap ruffian and a swearing Iacke.
Phr. to play the jack: to play the knave, to do a mean trick. Obs.
1610 SHAKES. Temp. IV. i. 198 Your Fairy..Has done little better then plaid the Iacke with us.

1611 BEAUM. & FL. Knt. Burn. Pestle Induct., If you were not resolved to play the Jacks, what need you study for new subjects, purposely to abuse your betters?

Jack Jones: rhyming slang for ‘alone’; usu. in phr. on one's Jack Jones: on one's own; alone.
1935 G. ORWELL Clergyman's Daughter ii. 156 A good night's kip all alone... All on your Jack Jones.

Colloq. phr. I'm all right, Jack: a saying indicating selfish complacency on the part of the speaker.
1910 D. W. BONE Brassbounder iii. 37 It's ‘Damn you Jack - I'm all right!’ with you chaps.

1919 F. NINETTE Tiddley Sailors 26 They dodged as much work as possible and generally assumed the manner ‘I'm all right Jack’.

Variously applied to a serving-man or male attendant, a labourer, a man who does odd jobs.
1836-7 DICKENS Sketches by Boz (1850) 59/2 Having a chat with the ‘jack,’ who..seems to be wholly incapable of doing anything but lounging about.

Jack the Lad colloq., a conspicuously self-assured, carefree, and often brash young man; a ‘chancer’.
c1840 (song-title) Jack's the lad. Ibid. (refrain) "For if ever fellow took delight in swigging, gigging, kissing, drinking, fighting, Damme I'll be bold to say that Jack's the lad."