that is not a connector, but a wire splice joint. the wire does not look like part of the stock wire bundle, either a replacment or perhaps something added by a previous owner to power up an accessory, or to by-pass a bad section of wire. You will have to trace where it goes.
It was probably a wire that a previous owner added to operate an aftermarket accessory of some sort. Are you having an issue that you think is caused by this wire? If not, I would just leave it alone.
It may be one of the ones that goes to the transmission. Is this on a manual? I think the wires going to the trans are for the 4WD indicator and something else. Is the wire also kinda fat, as in not the usual 18 gauge?
Why yes it is of the more rigid style when compared to the thinkness of the others within its realm.all the 3 wires that go to tranny cluster are fairly thin .at least that is how they were when I found that my assistant (who I blame when things are forgotten are hooked up wrong )did not plug in the aforementioned cluster and we're slowly ground off one hop and scrape at a time
I used to laugh at the man with a pinto , until I became a humble servicer of a tercel