Of all my seven currently used online,this one is way the oldest and was invented before the internet was invented.
Way back inte very early 1990's, I (as a early 20 something) went to the local games arcade to play coin operated games. When I got a score to put on a hi-score table, I used "LNZ".
The name comes from the natural logarithm of complex argument and I first saw this function in complex form in a maths text book in October 1990. In January 1991, I adopted the shortened form of the equation as a arcade game hi-score table. If you are too young, these late 1980's-early 1990's games only gave you a three letter name for you to enter.
Ln(z) = Ln(x+iy) = 0.5*ln(x*x+y*y) + (2*k*pi + theta)*i
k = any integer
i = square root of -1
pi = constant "pi" = 3.1415926535.....
tan(theta)=y/x, -pi <= theta <= pi
For the curious:
Ln(-1) = (2*k+1)*pi*i
If k=0 (principal value), ln(-1)=i*pi
Or exp(i*pi)=-1 which is famously stated as:
exp(i*pi)+1 = 0, which is Lenoard Eulers most famous ever formula!