This is the 18205th most frequent Russian word.
чемоданом
"Чемоданом" means "by/with a suitcase" in English.
Here, 'чемоданом' (transliteration: 'chemodanom') is the instrumental case singular, used to denote the means or tool, such as traveling with a suitcase.
Я путешествую с большим чемоданом.
I am traveling with a large suitcase.
Here, 'чемоданом' is employed in the instrumental case singular to describe the subject as being in association with an action - convenience when using the suitcase.
Её чемоданом удобно пользоваться.
Her suitcase is convenient to use.
In this instance, 'чемоданом' is in the instrumental case singular, illustrating the method or medium used to send the documents - through a suitcase.