This is the 5206th most frequent Russian word.
ногам
"Ногам" means "to the legs" in English.
The word 'ногах' is in the prepositional case and is used to indicate the location ('in my legs').
Я чувствую усталость в ногах после долгой прогулки.
I feel tiredness in my legs after a long walk.
Here, 'ногах' also appears in the prepositional case to talk about a condition or feeling ('pain in legs').
Она все время жалуется на боль в ногах.
She complains all the time about pain in her legs.
In this sentence, 'ноги' is in the accusative case used after a verb of motion ('to stand on one's feet').