@mhoye Found it. Patrick Juola was the guy. 1998, categorizing the complexity of languages by gzipping them. https://scholar.google.co.uk/scholar?q=patrick+juola+complexity+compression&hl=en&as_sdt=0&as_vis=1&oi=scholart#d=gs_qabs&t=1689286759338&u=%23p%3DbcHXg7kuXAIJ