This is the 4330th most frequent Polish word.
fordem
"Fordem" is the instrumental case of "ford," meaning "with/by a Ford (car)" in English.
The word 'fordem' here is used in the instrumental case to indicate the vehicle (a Ford) used to traverse the river.
Przejechałem przez rzekę fordem.
I crossed the river with a Ford.
In this sentence, 'fordem' is in the instrumental case, referring to the means of transportation, the Ford car.
Fordem pojechaliśmy na wakacje.
We went on vacation with a Ford.
Here, 'fordem' describes the vehicle type using the instrumental case, indicating enjoyable experience with a Ford car.