having a sore back, usually a country term

A variation on "Down To Fuck," Down to Not Text Back implies a girl that will most definitely not return your digital advances. Usually, this situation can be transparent. However, the worst cases occur when you get totally played and blindsided by a girl who's seemingly really really really into you.

A person who essentially has went through life unnoticed and in the background of society. Is more than likely a virgin.

It means that you winning in everything against anyone, no man stands a chance.

A line of flavor text when fighting Sans that might pop up, the protagonist is described as 'feeling their sins crawling down their back'.

Other words can be transplanted into it.
Undertale

to be a coward, to be cowardly

something you say when someone lies to you, cheats on you, betrays you