The = symbol that is now universally accepted by mathematics for equality was first recorded by Welsh mathematician Robert Recorde in The Whetstone of Witte (1557)... to avoid dthe tedious repetition of theses words: "is equal to", I will set (as I do often in work use) a pair of parallels, or Gemowe lines, of one length, because no two things can be more equal.
The oppsosite function would be the not equal sign≠ . Which is an equal sign "=" with a slash "/" through it.