I first encountered this word in troff documentation back in the 1980s. Two examples:
A Typesetter-independent TROFF by Brian W. Kernighan, 1982. https://www.hack.org/mc/texts/ditroff-kernighan.ps.gz
Using nroff and troff on the Sun Workstation, 1986. http://www.bitsavers.org/pdf/sun/sunos/3.0/800-1321-03A_Usin...