This is the 8387th most frequent Russian word.
мужчинам
"Мужчинам" means "to men" (dative plural form of "мужчина").
The word "мужчинам" is used here as the dative plural of "мужчина" and indicates the indirect object of the verb "дал" (gave), the recipients of the books.
Я дал мужчинам книги.
I gave the men books.
The word "мужчинам" in this sentence represents the dative plural form of "мужчина," used to show the beneficiaries of the help being described.
Помощь мужчинам была важна.
Help for the men was important.
The word "мужчинам" is used as the dative plural form of "мужчина" to indicate the intended recipients of the presents being sent.