What does the ABC stand for in standard form Ax+By=C?

What does the ABC stand for in standard form Ax+By=C?

$Ax+By+C$ is a generalized form (in fact the standard generalized form) for a linear equation
where $A, B, and C$ are placeholders for constants (the $x$ and $y$ are variables).
The generalized form, $Ax+By+C$, includes equations such as
$color(white)(XXXXX)$$7x+3y=98$
$color(white)(XXXXX)$$(1)x+(-5)y=14$
$color(white)(XXXXX)$$9261x+83y=-7491$
$color(white)(XXXXX)$$color(white)(XXXXX)$any infinitely many others
By normal usage $A$ should be an integer value which is not negative.

ncG1vNJzZmign6zBsLDIrJquq6NjsLC5jq1msKCRqXqlu8SsZK2glWKuo6%2BMrKuappRis7C%2BjKKlZquklrulrdGdZJ%2BnoqJ6osSMm7Bmm19mgXqClQ%3D%3D