Maentwrog is an RPN-calculator-turned-FORTH-interpreter which probably counts as Chris Pressey's first proper programming language. It was implemented on his Amiga 500 in 1993, then lost and unearthed multiple times. It is hardly remarkable, save that it spawned Befunge-93.
*a *b *c 0 =a 1 =b : fib a b + =c c . b =a c =b c 100000 < @fib ; 1 . fib
maentw.c in the Maentwrog distribution