What a cool gift. I didn't know Knuth was into Sanskrit poetry. Nice to notice that people from STEM fields are interested in things like that. I'm always happy to see something related to ancient languages in HN.
https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_form
The idea of describing the structure of language using rewriting rules can be traced back to at least the work of Pāṇini (ancient Indian Sanskrit grammarian and a revered scholar in Hinduism who lived sometime between the 7th and 4th century BCE).[1][2] His notation to describe Sanskrit word structure notation is equivalent in power to that of Backus and has many similar properties.
Citation:
https://dl.acm.org/citation.cfm?id=363165
I can't copy the text here, but it's worth a read:
https://www.deepdyve.com/lp/association-for-computing-machin...
Knuth is mentioned in the same letter as Panini, regarding the naming of "BNF".
https://www.infinityfoundation.com/mandala/t_es/t_es_rao-t_s...
Knuth invented LR parsing of context free grammars:
https://en.wikipedia.org/wiki/LR_parser
LR parsers were invented by Donald Knuth in 1965 as an efficient generalization of precedence parsers. Knuth proved that LR parsers were the most general-purpose parsers possible that would still be efficient in the worst cases.
https://web.stanford.edu/~kiparsky/Papers/panini-1.pdf
My Knuth tale: I happened to be sitting near Prof. Knuth at a dinner last December and I mentioned to him Pāṇini & Sanskrit in the context of something I work on now and then. He heard Sanskrit and immediately pointed me to this Christmas lecture of his!