Kaete Sidh, budh, nath, ketey ketey devi ves
There are many Siddhas, Buddhas and Nathas.....
(Japu, p. 7)
The word Buddha seems to have been used for Gautama Buddha, the founder of Buddhism.
1. Kohli, Surindar Singh ed, Dictionary of Mythological References in Guru Granth Sahib, 1993