ни бельмеса

(не знать, не понимать, не смыслить и т. п.)

прост.

not know a thing; not have a clue; have no idea about smth.; not have an inkling of anything; cf. not know 'a' from 'b'; not know a B from a battledore (from a bull's foot, from a buffalo foot, from a broomstick); not know chalk from cheese; not know beans

- Вот ты всегда утверждал, что я глуп, ей-богу, брат, есть глупее меня! Теперь в направление полез; сам ни бельмеса не чувствует, ну, а я, разумеется, поощряю... (Ф. Достоевский, Преступление и наказание) — 'You always maintained that I was a fool, but by Jove, my boy, there are greater fools than I am! Now he is setting up for being advanced, not that he has an inkling of anything, but, of course, I encourage him.'