This is the 1238th most frequent Russian word.
ничем
"Ничем" means "by/with nothing."
The word 'ничем' in this sentence acts as an instrumental form of 'ничто' (nothing), indicating inability to contribute any assistance.
Я ничем не могу вам помочь.
I cannot help you with anything.
Here, 'ничем' is used to express the absence of distinction or difference in relation to others.
Он ничем не отличается от других.
He does not differ in any way from others.
In this context, 'ничем' denotes the lack of interest in any particular subject or activity.