Green’s Dictionary of Slang

1. the tip of the penis.

1961		Partridge DSUE (5 edn) 1079/2: The glans penis; mostly in compounds: bell-end,blunt end, red end: esp. Services’: C 20.
1984		McConville & Shearlaw Slanguage of Sex.
1988		J. McDonald Dict. of Obscenity etc. 10: For added vividness a bell-end is sometimes called a cheesy bell-end.
1998		K. Sampson Awaydays 78: Alternating deep draughts which take my entire length inside her with delicate tongue jobs on my bell.
1999		K. Sampson Powder 380: Teasing himself in the shower, deluging his numb bell-end with the scalding needles.
2000		M. Manning Get Your Cock Out 32: Freeloaders [...] snorting lines of cocaine from each others’ naked breasts and straining bell enders.
2003		‘Rev. of Enge Teeny-Saue’ on YourChoice.co.uk 🌐 Commuter Tonia [...] sweet talked into parking in the woods. Tongue tweaking her small, hard nipples has the desired effect; her lips wrapped ’round his knob [...] his spunk spurting into her mouth from his engorged, purple bell end.
2012		(con. 1980s) I. Welsh Skagboys 84: Ah kin still git the bell-end n even a bit ay the shaft on a good day.
2015		I. Welsh Decent Ride 279: A strand of pre-cum hanging from bottom lip to the bell end of Terry’s cock.
2023		R. Milward Man-Eating Typewriter 189: A glittering bell-end of silver throbbering atop a smooth shaft.

2. thus, a general term of abuse.

1992		rec.sport.soccer (Usenet) 28 Sept. 🌐 Perhaps you are referring ot that infamous collection of bellends known as w.b.a. (win bugger all.
1998		K. Sampson Awaydays 33: Them bell-ends. Been caning it down.
2001		OnLine Dict. of Playground Sl. 🌐 bell-end n. [...] 2. An excessively stupid or unpleasant person. [Ibid.] bell-ender n. A wanker.
2009		T. Black Gutted 40: Simon Cowell tearing into some utterly deluded bell-end of about sixteen.
2013		K. Sampson Killing Pool 279: Let the pair of bell-ends tear lumps out of each other, far as I’m concerned.
2017		Huffington Post 27 Aug. 🌐 You’re [i.e. Donald trump] a bellend mate.