On “ngas” in “brjed ngas pa”

Recently Nicola Bajetta was wondering what ngas in brjed ngas pa could mean. I had no clue either. We looked up Jäschke. The first meaning (i.e., instrumental of nga) is irrelevant and uninteresting. The second is ngas in mi ngas (occurring in Tāranātha’s rGya gar chos ’gyung), to which he states: “is undoubtedly a typographical error,” that is, for mi nad. He also points out that Schiefner, who translated the rGya gar chos ’byung, “has left it without an annotation.” We then looked up bTsan-lha’s brDa dkrol (s.v. ngas), which gives thal ches pa and thal drags pa as its meaning. Interestingly bTsan-lha records here brjed ngas, brtun ngas, and mu ngas. bTsan-lha’s meanings have been noted by Dung-dkar and Dan Martin as well. Of course, we know that  brjed ngas pa (TSD) renders the Sanskrit vismaraṇa, saṃpramoṣa, vismṛta, muṣitasmṛti, etc. In short, brjed ngas pa, as a noun, would mean “forgetfulness” and if it is an adjectival verb, as it seems to be, it would be something like “to be forgetful.” Second, brtun ngas pa is supposed to render rabhasa (TSD), “impetuous, violent” and “impetuosity, vehemence” (MW). Third, mi ngas is said to render māri (→Udrāyaṇāvadāna), “pestilence.” Tibetan dictionaries also record it as a lexeme. In this case,  Jäschke is both right and wrong. He is right because mi ngas has been glossed as a kind of mi nad. But he is wrong because mi ngas is certainly not a typographical error. A search in the BDRC yields several instances where the word seems to be used either in the sense of “pestilence” or of some kind of “calamity.” Now the question is: What is the common semantic element in these three words expressed by ngas? bTsan-lha’s meaning does not seem to work here. I also cannot account for his mu ngas. Perhaps, this is an error for mi ngas? He seems to have deduced the meaning of ngas wrongly. In my view, ngas in the first two words seems to carry the semantic weight of “to have the likeliness/tendency” or “to be prone to” (something). Thus, brjed ngas pa seems to mean something like “to have the likeliness/tendency to forget” and brtun ngas pa “to have the tendency to explode” (i.e., to have the tendency to lose one’s temper). What about mi ngas pa? I must admit that my explanation does not work well with this. Perhaps “to have the potential to [cause disaster to] humans”? I wish I had a better explanation.

Postscript: As pointed out by Chung-tshe-ring brjed ngas has also been spelled brjed ngad. This can be confirmed by searching the BDRC. What is, however, note worthy is that this spelling does not seem to occur in allochthonous Tibetan sources but does so only in some autochthonous Tibetan sources. Of course, the various shades of the meaning of ngad have been well documented. The question is whether brjed ngad pa is simply an orthographical/typographical error for brjed ngas pa, or, whether it is an acceptable orthographical variant. If it is an acceptable orthographical variant, the meaning nus pa might work best here. That is, brjed ngad pa might mean something like “to have the potency/potentiality (i.e., tendency) to forget.”