I also found it weird that simple words were translated in great detail in the tipitaka, eg old age in Mahasatipatthana sutta, but not more complex words like anatta
Katamā ca, bhikkhave, jarā? Yā tesaṃ tesaṃ sattānaṃ tamhi tamhi sattanikāye jarā jīraṇatā khaṇḍiccaṃ pāliccaṃ valittacatā āyuno saṃhāni indriyānaṃ paripāko, ayaṃ vuccati, bhikkhave, jarā. |
And what, monks, is old age? If there is old age for all kinds of beings in whatever kind of existence, their getting frail and decrepit, the breaking [of their teeth], their becoming grey and wrinkled, the running down of their life span, the deterioration of their sense faculties – this, monks, is called old age. |
If i were to try and reason it, it could be the case that there was no need to translate them. Let’s say I write a book now and say “the future is unpredictable”. Need I explain “unpredictable”? But let’s say 2500 years later, when technologies improve, things are almost fully predictable, there may be no more words to fully capture this meaning of unpredictability.
I heard of linguistic studies to show that the words in the language we speak reflects the culture and its focus. I do not have the study, but one example I can raise is “Karoshi”, which means death by overwork in Japanese. This word exists for them but not in english because it is more common in Japan.
Likewise, anatta maybe more common in Buddha’s time, and the culture would have more easily grasped the word, so it could have been not necessary to explain it.