Like hell is 'the ick' a mumsnet word! 
I have heard it for YEARS now. Even FRIENDS had an episode called 'The one with the ick factor.'
One experience I have where I got the ICK factor... I was 17 and a guy I met in the pub asked me out. He was about four or five years older than me and he only lived about 10 minutes walk away. We went to the pub three or four days later and then about 10:00 o'clock at night we came back to my house/my parents house and went into the dining room and sat on the couch.
He put his arm around my waist, and to the size 10, '25 inch waist,' 9 stone, 17 year old me, he squeezed my waist and said 'oooh, you've got a little bunch of fat there ha ha ha... I think you can pinch more than an inch can't you.' 9 stone with a 25 inch waist I was. And he totally fat shamed me on our first 'date. I was not even remotely 'fat.'
I already had a bit of an issue about my weight as I'd been 11 and a half stone at school and bullied for my weight, and I had actually lost two and a half stone in a year, and was really proud of it. So my first date - the first guy that ever really properly asked me out - said to me when I was actually slim 'oh you have a bunch of fat there!' It sent me into a spiral of crash dieting to be honest with you as I thought I must still be too fat. I got to 7 stone 3, and my mom said that I was so wafer thin she feared for my health.
Absolute utter cunt, but yes I definitely got the ick factor after that .... I actually stood up and said 'get out of my house.' Baffled as to why I was throwing him out he said 'what..? what's up?' I said 'you basically just called me fat and said about fat all around my waist and that was nasty.' He couldn't seem to understand why I threw him and said he was 'joking.' Stupid cunt. He pestered me for weeks trying to get me to go out with him again, til my dad threatened him with the police.
A similar thing happened a few months later ... a bloke who was about seven or eight years older than me asked me out at work - he was 26 I was 18. I said 'I'm not sure.' He kept talking to me work and following me around constantly ...
I'm not kidding you, this one day, he stared at me across the canteen table and said 'you've 5 big spots on your face haven't you - really red and obvious. Spotty muldoon I'll call you.' I had fairly nice skin, and the 5 spots, were only there coz I was on my period, and I was a fucking TEENAGER. Another utter cunt.
What the actual F? Is this some kind of bizarre way of flirting or trying to get a woman interested, or just nasty-ass negging? I binned that fucker off too. I just walked off and refused to engage with him again.